Here is a suggestion I think for Simpleplanes' future update:

Designer:
1. In the Paint Job tab, Decals let you use PNG images from your computer file by filename and never take too much part count, they connected to more than one fuselage blocks, correctly curved automatically, you can add things like nosearts, roundels, flags, emblems, kill scores, numbers, texts similar to labels rather than using SPRastermatic so you can look at your image for clearer without too pixelated so you won't have to worry about why it is too pixelated. The Decals when placing on both the wing and the rudder can move too without glitching out so you also don't need to worry about it.
2. Custom-paint mode can let you paint the entire craft by make liveries like drawing a cheatlines, camouflages, signatures. You can also draw a livery like example; making a livery of a US Air Force One, Antonov Airlines livery or Tropical Livery instead of using Fuselage blocks to reduce part count. Same to Decals, the custom liveries on the tail or wings can move by the control surface without glitching it so you will not have to worry about it.
3. New parts like people you can add like fighter pilots, airline pilots, passengers, military soliders, navy officers, WW1/WW2 Pilots, Police Officers, Firefighters, EMTs, Civilians and have a custom clothing for them, you can customize their clothes from winter coats to, swimwear, to uniforms and civilian clothes, they can be changed from Male to Female, sizes can be ranged from Child, to Teen or Adult, maybe aliens can be added in too. Animals/Mammals/Creatures can be in too like Cats, Dogs, Squirrels, Eagles, Dragons, Dinosaurs, Unicorns. Click on any person in the people menu to take control of too
4. Functionable custom wipers can be added to in the designer and when you play it, you can activate any Activation Group for the wipers to move like during the rain.
5. More weapons like Machine Guns, Laser Guns, Pulse Lasers, Flamegun, Laser Cannons, Photon Torpedo, Multi-role Missiles like from Ace Combat, Napalm Bombs, Bomblet Dispensers, Fragmentation Bombs, ECM Pods, Multi-lock Missiles, Ripple lasers, Plasmas, Mass-Drivers, Charge Laser, Mines, Railguns, Wave Shot, Burst Missiles. Gun bullets can range from, Electric Explosive, flammable can set things on fire, normal, freeze bullets can freeze things. Guns and missiles can have custom sound effects like example a laser gun to sound like TIE Fighter's laser.
6. Aside for adding people in the game, items and weapons come in too like Shotgun, Rifles, SMGs, Assault Rifles, Pistols, Bows, Swords, Daggers, First-Aid Kits, Fire Extinguishers, Flamethrowers, Flashlights, Flares. Firearms can be reloadable too by changing to limit ammo, they can also damage anything like Fuselage Blocks, and craft's parts
7. Additional parts for cars like custom Car Engine sounds can be like from V6s, V8s, Electric, Hybrid, V12s, VTECs, Inline-8s, Flat-12s, Diesel Engines, you can change the litres to make the sound different only on some engine sounds like 5.0L, 2.0L. Transmission mode (Except for Electric) can be set from auto to manual and customize the speed from 1-3 speed, 1-4 speed, 1-5 speed, 1-6 speed and with any number of speeds. Manual can be set from using the desired keys on the UI during gameplay to change the speed, any keys assigned to it when pressing brake and accelerating, you may hear revving like how race cars do. A 2 connect-point resizable wheel can be mostly used for Motorcycles too.
8. Customizing plane engines like Rotors and Propellers can be customizable so can change its appearance using "Custom" on the Blade Style so you can change its look to make it realistic, Turbo sounds can be added on to it as well, you can change the propeller engine from single or contra (Like the TU-95). For jet engines, you can customize its cowlings and its appearance to make it look different. Custom sounds can be used by using OGG format sound files and customize them in with the pitch and volume, you can have multiple sound files in it like example fighter jets where the first OGG was silenced when the second OGG (Afterburner sound) was played, you can change it using the throttle and click to action button so the effect can sound correctly, Activation Groups can be set on as well. The jet/propeller/rotor engines will idle instead of switching your throttle from 0% to max or just customizing the other engine to 0 Power Multiplier only on Custom/Idle engine mode rather than Simple mode. Custom/Idle engine mode can shut down when you deactivate the Action Group like example "Action Group 8".
9. If you want to make the plane like example CV-990 to CV-880, it may be difficult, stressful or a lazy to do but let the thing in game to do for you like some sort of AI or something, same when trying to make a Tu-104 either Tu-110 or TU-117, don't tell anyone about it.
10. If you don't like the Primary wings, Stabilizers and Structural Wings to be so blocky and simple, you can change it making it curve. Additionally, the wings can have multi points so you can make airliner wings, you can also customize the number of flap fairings only for airliners too. You can customize their shape using advanced curving like for example curving a vertical stabilizer to make it look like A6M Zero's tail. Another one is where you can cut the shape by making clipped wings. You can also add the "Krueger Flap too on the Primary Wing." Radiators like these can be added under the wing like BF-109 or Fiat G.55 Silurante.
11. You can also use custom-cockpits by changing its appearance through points so you can try to make it look realistic like making it look like P-40's cockpit of a Bubble canopy like the P-51D Mustang or make it like the Mig-31, F-117 Nighthawk, SR-71 or F-1111 Aardvark. Some custom parts with noses is a custom passenger cockpit where you can make it look Boeing, Airbus, Embraer, Cessna, etc. It's up to you that can make a C172 Skyhawk, Airbus A320, Tu-104, Tu-204, L-1049, CV990, Boeing 737, Boeing 747, Shanghai Y-10, A220, etc. Supersonic Cockpits with droop snoot mechanism like only for Concorde with custom visors, some like Tu-144, L2000, B2707, these parts can be customizable like the glasses too. If you don't want a droop snoot mechanism, you can select the "Droop Snoot" and it will be a fixed supersonic nose so you can make like Aerion AS2 or LAPCAT A2.
12. Don't need the wheels for your rides to the future? You can add those like Anti-Gravity parts under your craft to make it like possibly a "Flying Car" which hovers on the track, it can be optional whenever roll effect can be used to make your craft roll slightly a little when turning or doing a barrel when you reach the mid-air until you landed, nothing to worry as these anti-gravity parts lets you hover instead of crashing to the ground after landing, you can pitch up or down but you never ascend and descend just like wheelie and stoppie of a motorcycle. You can also turn the vehicle too, also there is an addition to using a unique jet engine which acts like a car engine and can be optional with the Afterburning effect like futuristic racing car games.
13. Some special Fuselage Blocks can also come in additional light-up windows for your planes like passenger aircraft, you can change the size and the lighting colours for each of the windows. Hollow Fuselage Blocks can have moving doors too like airliners or cargo planes and you can change the size, dimensions, distance for the doors to move, you can customize the doors open/close mechanism making a folding door too.
14. You can add flags/banners like adding a flagpole and a flag and customize it's look by using your own custom-made flag from either website images or your computer files like example a flag of Venice, medieval banners, Racing Flags, Triangular Flags, Nepal Flag, etc. If you want to make a flag fly-by you can add a flag with connector behind or under the plane/helicopter like your country's Independence Day. Or add to vehicles like tanks, they can wave too when you customize the wind speed for your flag or just simply do a fly by and your flag can wave too, same when you drive a vehicle.
15. Instead of using parts for submarines to submerge and the part intact on the water keeps afloat, you can use submersible parts to make you submarine go underwater but you need an Underwater Camera Mod. You can also make things like sinking ship/boat scenarios too.
15. Boat/ship/submarine parts like hydrofoils, lifeboats, lifebouys, hulls rudders, bow thrusters and engines/propellers, these engines can move your ship instead of using planes' engines underwater. you can also make amphibious cars/tanks, jetski, hydrofoils, boats, cargo ships, oil tankers, cruise ships, ocean liners, car carriers, bulk carriers, fishing vessels, lifeboats.
16. Radios and GPWS can also be added to the craft, GPWS only tells pilot to pullup only if their plane is crashing to the ground or water if the gear is already retracted. Radio is where you can add your own songs in MP3 or WAV and can either be looped or not looped, volume can be changeable too.

Uploading crafts

• Before uploading the plane, the plane will auto-detect from which the original creator made the plane before auto-crediting, before publishing it has to be checked carefully 100% to analyse the difference between the original and the custom-painted, tweaked, updated or with different variant, or major changes, similar to YouTube's Copyright Checks when publishing it from game or from unlisted builds, some players do typed in the credits to the original user and changes to the appearance of their crafts on the description before publishing it, if the plane is almost same look a question will be given to the user who modified it is it the same build or modified, if so, the analysing of the aircraft will be commenced instead of being taken down instantly, checking the looks, checking XML edits to any changes or if there if items like labels, it will be taken down if the plane is probably the same as the originals. Apart from that, if the post was removed, instead of commenting, a note just like from DeviantArt will tell you about why your post is removed which broke the rules like "Misleading Thumbnails, Sympathy or Memorial posts, no major changes to the planes' appearances (Livery, parts of adding more weapons), those referring to bad histories like plane crashes".

You can also transfer your custom painted craft from Simpleplanes 2 to the original Simpleplanes and it doesn't have any problems

Gameplay:
1. You can make some Simpleplanes Minimovies with the help of Scenario Designer mode where you can look at the open world, you can pan the camera and go to any locations like Wright Isles, Snowstone, Maywar, looking to the Brown Pearl, the Kraken and etc. you load some planes and place them anywhere into the scene, draw a path for your craft and add activation group on the scene. Nothing to worry during the making because your craft maybe in the correct route when following the path during your making. After finished, you can view the movie or screenshot it, you can also add voices, texts and sound effects in the making too.
2. More places to go, like more islands from small to big with destructible buildings, castles, bridges, houses and Igloos. Maps do have those like mountains, fortresses, shipyards, docks, cities, towns, temples, towers, futuristic places, train stations, air bases and airports.
3. Passenger/Cargo plane missions can be played when you only select a large or small passenger, Cargo plane, take off, land and taxi. If the plane crashes, the level will fail. Follow the route by flying through the hoop indicating the flight path by the arrow. The rules are no weapons allowed, avoid flying upside down.
4. Tank battle missions can allow you to drive a wheeled armed vehicle like tanks, SPAA, Tank destroyers. destroy all enemy vehicles you see here and don't get destroyed or the mission will fail.
5. If you select "Full weapons mode", you will fire all weapons instead of firing one by one.
6. If you don't want the Ice Base to attack you or enemies to fight back against you after fire weapons, you can go to settings and switch enemy combat off via menu's settings. Only in Sandbox mode.
7. Cheat mode like you can switch from infinite fuel, undamageable/indestructible parts, only in Sandbox mode.
8. Changing the AI craft mode from enemy (Green/Red) to friendly (Blue)
9. AI craft's path can be customized, and looping can be on too like example in Sky Park City Gold Prix Raceway, you draw a path for the AI Racer, and you feel like you can race with others. You can make the AIs in Wingman mode like protecting your plane like covering you, disperse to any targets to engage at their discretion, attack enemies in front of player's craft like Ace Combat, you can customize their path too like performing air shows.
10. People Parts can be AI active when they can do their own thing or simply customize it making them walk or run, swim, jump etc. especially sitting or standing up.