[xwiki-users] Ability to rename users?

Hi, I've realised that for my project it would be ideal if users had the ability to change their login names. You know the kind of thing, you register on the site as crazygirlLOL and then your boss shows up and you want to be renamed as maryc. I've had a look around and can't see that XWiki supports this. I bet it'd be a pain to implement, changing all the history and group memberships and permissions and whatnot. But if there's nothing out of the box it looks like I'll have to write this feature myself. Any suggestions? P.S., I saw a reference in one of the macros to allowing user pages to exist in spaces other than XWiki in the future. That would be useful too, and probably touches much of the same code.