At first: I'ts a good game, nice to play. Good graphics. Keep up the good work!

I want the player to be able to steer helicopters
Sounds like the good old dos game Seek and Destroy. You control a heli moslty, but there are some tank missions.
Like Seek and Destroy it would be cool to pickup friendly units from an enemy camp and drop them back at your base (start point).

Here are some screenshots:
http://www.mobygames.com/game/dos/se...oy/screenshots