You must play drastically different than I do. I usually play Dante/Vergil/Dormammu or Morrigan and I do not use the "charge". Even if I did, I could manage on the face buttons without moving it.
I can still play UMvC3 on a level near what I can play on PS3 with my stick. My SFxT ability is drastically reduced though -- from missed supers to the inability to vary my projectile speeds, I have ridiculous amounts of trouble using the L button with a motion on the d-pad... my left hand just can't manage it... I've never changed the button layout for UMvC3 Vita and never will.