I think the weekly sticky is a good idea, but leaving it to a vote could be problematic in the future (maybe OK for now). I think, eventually, Team Snapzu should promote tribes on the front page or in the lounge based on stats and a quality assessment.
Maybe you can look at how reddit does it for some ideas (read the sidebar).
In any case, I'm looking forward to it!
Why do you think that it would be problematic?
And I'm aware of /r/subredditoftheday. Though I'm not sure if they have a method to it. I think they just pick it. I want this to be merit based.