one thing that i feel absolutely essential is that they have exp curves, mixing for flaperons etc, and a way to assign any channel to any switch/lever, so i can maybe change 2 controls, (like flaps and spoilers) without having to open up the model and manually switching the connectors on the reciever.....

A 6 position switch would be fantastic! (hope this qualifies as a 'necessity'). I'm sure APM users will agree with me...