I just feel that it would be cool to vary your personal mappool a bit by being able to play certain maps vs certain races (cyber forest for instance is a cool map, exept for pvz). I know, there would be comments like "take it like a man and don't veto anything", but since veto system is already in game as a legit tool, why not make it more flexible.
Edit: about my previous suggestion on specific MU (not map) veto system.
Intorduce a new game mode (lets call it "practice tool or w/e"), where you can que (separetely from ranked) with certain MUs checked/unchecked. System searches for the opponent (who qued using that new mode (again, not ranked!!!) using your ranked/unranked MMR, but doesn't change your MMR regardless of the outcome.
So, basically, it could be just a custom/melee autofinder. I just don't get what's so difficult about it from a coder perspective.