Vaizard are, to my knowledge, neutral.
Though tend to kill hollow more than shinigami maybe.
ok, a hollow.
you would then normally walk between shinigami... kill souls, devour then...just the normal stuff, while you walk through, you greet the ...hm, strange, why do you get attacked by shinigami all the time...

nah, a hollow is not possible, also quite too weak.
I would have to do 2 different games, same on SL with Orochimaru... if you play a Sound, and it should be a subordinate, you will *never* simply visit Konoha, do normal stuff and leave. You'd be found+hunted down.