Customisable cannons, caliber, length, ammo count, reload rate, muzzle flash, and the rounds exploding when the hit anything (terrain, ground targets(which there should be more of), or air targets).
Also, there should at some point be multiplayer integrated into the game, so iOS can play multiplayer.
Also, maybe tutorials on how to build VTOL planes and helicopters, so that it isn’t hard to understand for new players.
Also different cockpit options, so the HUD can be changed depending on which generation of plane you chose, and the option to set a vehicle as a ground vehicle, instead of an aircraft, so that ai know to shoot a plane as if they were a ground target rather than trying to fly it to the player if it’s a tank for example.
More missions, maybe ai attacking the USS Beast and the destroyers so that you can intercept them.