I think marking all the functions on the controller makes a lot of sense and is a requirement for RPAS I thought.
I like your idea. Super! Going to fit that diversity screen of mine and Samsung Galaxy as well. And give the iPad to the cameraman.
I think marking the stick functions is hardly a RPAS requirement. If you can't fly without having to be reminded what the stick functions are you should not be flying, it should be second nature. As for putting them on there so you can hand it over to anyone else who does not have the most basic model flying skills is irresponsible. It really is not a 'TOY'!