Hmmm ... I thought you said the models were generated in code before using algorithmic poly ops.
Also about the control this is what I was thinking.
Left stick or WASD to move forward and strafe. Right stick or mouse left to right for yaw and push the right stick up and down or one of the mouse buttons to change elevation. Maybe mouse wheel for elevation change. It seems that with a helicopter you should be able to lock your elevation. If you don't like that though you can leave gravity to pull you down but still allow the player to increase elevation on a gamepad without pushing down a button and only by wiggling the analog sticks.
Also about the control this is what I was thinking.
Left stick or WASD to move forward and strafe. Right stick or mouse left to right for yaw and push the right stick up and down or one of the mouse buttons to change elevation. Maybe mouse wheel for elevation change. It seems that with a helicopter you should be able to lock your elevation. If you don't like that though you can leave gravity to pull you down but still allow the player to increase elevation on a gamepad without pushing down a button and only by wiggling the analog sticks.