Devs have to provide a map for the button configuration on vita. Let's take, for example, something like COD. I reckon devs would have to do something like this.
Circle - Circle
Triangle - Triangle
Square - Square
X - X
R1 - R
L1 - L
L2 - Touching left half of back touchpad
R2 - Touching right half of back touchpad
L3 - holding anywhere on the front touchpad
R3 - swiping ( or tapping ) the front touch pad
Could work, though it could be very uncomfortable playing COD with that set up. Maybe if you get a grip for vita? Sony should really release a vita tablet with an attachable pad that includes R2/L2 buttons.
The vita sticks aren't pushable?