What it might be worth doing is collecting the various threads together in this forum, which will give a good idea of how many there are and they won't get lost in the general forum.
Hm, see now that makes me wonder if moving competitions here at all is a good idea - I mean sure you'll be able to find them if they're in CC or their own subforum, but they won't get the exposure they normally would in General.
Certainly whole composing the competition entries it would make sense to post a thread here, but once composted the actual voting should probably happen in General.
My concern about a sub-forum is that the active threads can get buried (although I'm not sure how SMF does them but I don't think they show on the main page but it has been a while since I checked). I think your suggestion of stickying the current active threads is a good solution, for now.
This is true, SMF is like any other forum were active topics (those recently posted in) are bumped to the top, and ones with few replys descend off the bottom into the abyss.
Perhaps the solution
is to sticky them in General for their active duration, though this would require some pro-active moderation I can't afford to do.
Again, who normally composes competitions? Is any one person in charge, is it ad-hoc whoever feels like doing one..?