It will die down very quickly, as people become used it.
No point in creating a child board in the interim.
Exactly! Overtime, users will have to accept the fact that merit system will be here. They will have to adapt with merit system by changing their threads' contents to be more constructive. Less threads/ topics which cry and moan about merit system in the future, I believe it.
Whether or not they accept it isn't really the issue. It's a part of the forum, and a cool part of the forum that is heavily discussed. The only real argument I could see against it is that it could open a can of worms where users also want a trust child board to discuss trust issues and another child board for activity, etc. Perhaps that would be too many boards, and then there'd be nothing left to post about in meta.
So why not make a child board for trust system, merit,activity,etc... and take all of those topics from meta to that one. Hitting 3 birds with one stone. Meta would then remain solely for user problems and discussion.