What Id like to see is a setup SIMILAR to the aop/etc lists in that you would have a tab (somewhere - maybe address book [as current] or when you click on the TRUSTED button) where first you'd have a primary dropdown menu to select either extensions or nicknames. If you selected the file extensions you could add them like you can currently. If you choose the nickname list you could add a nickname, address, user level, internal list (aop/avoice/etc), etc. This way, the style would match some existing lists (not all of them) and would allow for greater manipulation (than current).
This is all just a thought, but in my mind, it would seem to make sence. Comment/create a better idea at will