i really think that it is necessary for there to be a way for Hollow characters to develop Hollow-ish powers outside of the arrancar resurrecion. that is, powers they can utilize in their Hollow and possibly adjuchas forms, and then perhaps later on in arrancar stuff. for example, shrieker could summon those exploding leeches or whatever from his mouth.
obviously, for maximum storyline awesomeness, original ideas would be needed, and for that to work, there would need to be admin/mod approval for such things.