I'm not demanding, nor bagging, but there are some stuff that in my opinion could make the game more versatile.

Flares: Everybody knows how awesome it would be if you had the chance to survive missile attacks with heavier designs. You should have max 2-3 shots, than you are on your own. ( to keep it fair.)

Rotor heads: We were granted the wheel and car engine, some of us asking for ship parts, but where are the Helicopter parts? A simple rotor head could cheer up the helifans which could get its power linked to a VTOL engine. Similar like wheel to car engine. Not every one of us is a XML god to cerate them on our own. (speaking of the good stuff, not a resized prop engine.)

Rearming station on airports: How fun it is to hunt and blow up some AI planes/ships/convoy around the island. But the joy ends fast because of the realistic limitations of your design. Yeah hitting restart is an option, but wouldn't it be more satisfying to have a spot on every airfield, where our contraption could get refueled/rearmed than continuing?

New weapons: Torpedoes or napalm strikes ( sorry mobile users, but i could not resist) could crack a smile on bored faces.