I've considered sub-boards, but because of the way SMF presents them (they are still visible from the main page) I'm afraid it would only confuse things further. Stickies and "collection" stickies with links to "important" posts are currently servicing the kind of organization you refer to. I'm not ruling out any possibilities, but for now I don't think sub-boards are the answer.
I'm still considering your "sponsored player" idea, just trying to figure out the best way to implement it.