AGAIN look at it in a bit wider perspective... As far as we can love IRC, and you can be used to it none of "modern"/new player give a flying poo about IRC, its good for clans/ setting match or talk with friends but probably more than half of players dont care about it and for most of time they go to server as a spec and talk from there watching other playing.
Most of players know each other from game... and most of them would like to keep it like that. Enter game, talk a bit about random stuff and then quit. Its typical online game friendship. Something like: "I like you, but GTFO after game".
Go to any game and see how look typical player want and use... and they prefer everything build in, they dont like jump from one app to another, they love stats , they love call your mom fat and they like quick action game that doesn't need any complicated systems just to play and talk. And after game end... they dont care.
So going to my point, Im not fan of lobby chat because I dont understand this idea at all, but lots of people like it, and my idea, weird or impossible to do, would look like system where servers act like rooms, and after selecting server you can use chat of it and then decide to enter game. Admins/mods could kick them and ban just like normal players. There could be one server that would act like "main room" but It would be hard to keep it clean from spam.
Also it would need some simple profile system, even just a Nick Name sticked to HWID/IP that would also gather basic stats(number of kills/death/caps/fav map/gun)
But still as far as profile/stats system would be nice... global chat in lobby for me is useless. But lots of people like this idea so I dont care if it would be implemented or not.