The Meaning of Life, the Universe, and Everything.
Having a server running on Vita would be a nightmare.
1. Vita goes into sleep mode if not being used after a few minutes, so you have to basically keep your guy moving or a button held down with rubber band or something else to make you spin or walk into a wall.
2. Vita will go into ad hoc mode even if you minimize the game to just check messages, or use the Vita for ANYTHING else, browsing, going to home screen, checking PSN messages, checking trophies, etc. Then when it goes into ad hoc mode it kicks everyone.
Save yourself the headache and do not have an actual server running on VITA, just play with people when you are playing, and do not have it going when you are not playing.