status.net is great, but I would have federation where you can add a server as a source rather than just a user. Then if that server has a @fred, @fred would always be resolved to the @fred on that server. In conflicts, you should be able to resolve these conflicts and proxy names yourself. (my proof of concept doesn't do this)

Maybe even taking Diaspora and taking out everything except 140char status updates AND adding an API compatible with Twitter apps would be a better approach.

edit: clarity to first sentence.