Pretty simple mechanical addition, would just consist of adding a function to the capslock key that toggles the more limited controls you usually get by pressing shift.
Pros:
-Pretty intuitive--capslock corresponds to a toggling of shift for typing, so it follows somewhat naturally that it should also correspond to a toggling of shift for flight controls
-Would save a decent deal of labor for players who use shift controls a lot
-Probably not super difficult to implement
Cons:
-Like all additions, it would require some coding

