World variables would be good.

As in you can set weight to 50% and everything you add to a plane would have 50% weight (great for those really big builds) or set engine power for 150% and all engines you add would have 150% power.

That sort of thing.

Also, have randomly generated islands along with the standard islands or use a 'seed' system like Minecraft does, keeping one Island/landing strip as 'always there'.