If you play MP then there's a cost associated with tweaking the game. Each MP mod out there breaks up the pool of available players and reduces the number of opponents you can play against.
I doubt it would break the MP scene anymore than it current is. In theory yes it could. If say there was a few rebalance mods made and played.
But getting the really competitive crowd together to agree on a mod...they could get exactly the balance they want.
I only play SP, but I can see the sense in gearing a game for MP and letting us work on the great opportunities, instead of the other way around.
I only suggest this as I have for a long time b/c the Devs dont work at the pace the MP expects. Or does things they really want. etc etc.
B/c after all they are making their game as they want. If they want huge imbalances. So be it. It seems silly if you want a somewhat even playing field for competitive play. And it maybe wrong to make a game like that but if they want to, they are going to.
Making an "Official Competitive MP Mod" would allow those who play the game that way to get their better balance, faster. Even allow them to add maps designed just for their level of gameplay and what ever else they can want.
Maybe in the end they wont need it, much like the TSOP isnt really needed right now, but if nothing it gives them the chance to play their way, while maybe showing anyone important what the MP crowd is looking for.