i think you have to no rush. is a good thought, but i really dont know if there is a real need to this on xmpp...

• for example for mail, there is obviously a real case use, both by the server receive email, and by the user. In xmpp by a fast thinking, found no use. Also in xmpp more things happen automatically by the clients, a right click on a name, an enter or an esc on some dialog, are fast interactions also happen only once. after that each user is known by its nick... So no obvious usage...
• also, taste matter most, but getgoogleoff is some how ugly for an xmpp account, while make a sense of other account cases
• same like address space, domain, accounts name, especially clean ones, are something valuable in web, and i think we're going to realise this more and more, as time pass
• who knows, if for example complete the new registration maybe need cute addresses to tied things between disroot, git.disroot, scribe.disroot, ( i mean what id user@scribe is not available for user@disroot user ... ), or what...
• i would propose to keep that aliases, ( dont waste any kind of space ), for maybe a future use.