Half-assed? Why the hell would you ever want to assign buttons to the touchscreen? All of the necessary buttons to play the game are available on the Vita there is no reason to tack on extra "cheat buttons" via the touchscreen. Terrible terrible idea. The touch mode is bad enough and should remain separate from the game proper.
Fighting games have no business using a touchscreen unless there is no other form of input available (ie - iOS).
Go back and read why. I explained it. It's not difficult to understand.