Great to see that you bring up this topic!
As I proposed before, I would really like to 'decouple' diaspora and webfinger. This way I could use webfinger on a domain I controll, and just specify in it (sort of delegate) which pod I host my diaspora account on. This way if we manage relations on the level of webfinger URIs, people can switch their pods like socks and just export/import data and update their webfinger files to reference current pod.
When it comes to 'moved to' new webfinger address, I see it as not diaspora specific and already started discussion on webfinger mailing list. Thread got bit mixed with other one buy my last suggestion you can find here:
https://groups.google.com/group/webfinger/msg/81e2b009e55bc724
Cheers!
=)
~ elf Pavlik ~