I couldn't resist making more suggestions so I had to.

I won't tag anyone like last time.

Boss Ideas:

1. Mothership
   [Located: Anywhere]
   [How to summon: set time to night and go up 100,000 feet]

[Spawn message: Something big has come down...]

[Behaviour: Laundhes missiles from the middle and has 4 turrets, 2 are MGs and 2 are AP Turrets, both turrets can tank 8 Cleaver missiles.]
[The boss itself can tank a LOT of hits.]
[Defeated message: They're gone now...]

2: Giant Submarine.
[Located: Spawn in Beast aircraft carrier and go 66666 Miles South until you see a black island]

[How to summon: go near it.]
[Spawn message: You have awoken the Submarine Titan.]

[Behaviour: shoots at you with it's 6 AA guns, 2 destroyer turrets and can launch large heat seeking missiles at you, if your using a boat it will also launch torpedoes at you]

[Twice the amount of HP than the Mothership]
[Defeated Message: None]

Boss for SimplePlanes 2:

1. Giant Tank.
   [Located: somewhere by the City]
   [How to summon: Use explosives on a small dot]

[Spawn Message: N/A]

[Behaviour: Shoots you with it's 4 MG turrets, the heavy MG turret on the tank turret and the Tank Turret itself, if your using a land vehicle it will try to run your vehicle over. The Tank is 3 times the size of the USS Tiny. The tank is like those water ATVs, can go in water.]

[Defeated Message: N/A]

And yeah, that's all I can think off.