How to get staged users offered in email-group-user-chooser

Another wacko question from pfaffman . . .

In a plugin with a custom Server model that belongs_to :user, I’m using {{email-group-user-chooser... in a template. It works!

Now I would like to be able to have that chooser include the ability to connect one of those Servers with a staged user. I can assign it by hand in the Rails console, but I can’t get the chooser to offer staged users. There is register_groups_callback_for_users_search_controller_action that seems to offer the ability to have additional groups show up. Is there some way to have it also be able to add staged users? I tried for a while to get it to return staged users, then backed up to getting it to let me add a random group, but failed even at that.

Is it worth trying to do pull in staged users that way or do I need to do . . … something else?