The biggest problem with teamstacking is when the server crashes. This has become more frequent lately, or possibly it's just the times I'm able to play. I find people like to do it when no one is there to police them, or even catch them doing it. Having a way to stop this would very much benefit the server.
There is also the unintentional stack which happens after a server crash. The teams are scrambled before even half the server is full most of the time, without anyone there to do it again, as admins are the only ones who can scramble on the first map.
I have to agree with Socks, the only real solution is to remove the ability to teamswitch, if it's possible just for the winning side so at least someone has a chance to help the losing team by switching.
