If this is considered, I would suggest that such a contest take a somewhat different approach than the recent 1vs1 tournament one did.

Basically, I think that there should be a rule (or at least, an agreement between all the judges) that the levels should be conservatively designed, with a very strong focus on balance, 2vs2 playability, dynamic gameplay, etc. Symmetry is not required, but the level should be carefully playtested (by both the creator and the judges) to ensure that it is not too lopsided. Gimmicks should be kept to a minimum but can be allowed if they aren't too extreme (in other words, no outright crazy stuff like Light Switch).

Those are the sorts of things you find in the current ladder mappool levels.
I think such a contest would be likely to produce at least one ladder worthy level. Of course, it's harder to design a level fitting such strict requirements, but most people who have made a few CTF levels are capable of that imo.