I don't know if what you're asking is possible, but there's a large vehicle mod with two different sets of flying controls for different helicopters. Unfortunately but I can't recall which one it is. Maybe have a look at the large vehicle overhaul mods (bdub's, vehicle madness, etc.) to see which one it is and then look at that mod's implementation?
So I have discovered gyrocopter plus. It doesn't give me the controls I was asking for, but it's a lot easier to fly (for me). It operates more like a regular helicopter than a gyrocopter. Can do vertical take off and landing. I like it.
If I am not mistaken, Rust has controls that just uses the mouse to fly. Left click is throttle to ascend and the pitch and roll is controlled with mouse. Yaw is missing, but you can still bank turn.
However yaw, is handled A and D. That is the simplest I can imagine it.