No performance meters in-game please, lol. I think Yoshi-P knows what he's talking about when he says he's absolutely certain it will lead to a bullying issue. I'd take it one step further and say it would lead to a community issue.

The way it is now is fine. It's easy enough to spot someone under performing and if they don't meet your standards in a PF or any other high-end content, you can kick them without making a big deal out of it.