Pretty simple, disable scoreboard before round starts for everyone (specs included). This could help prevent stacking in some cases or generally just less of pub stacks (stacks in which good players join the same team as other good players). Small change I know. yes you can get around it by using steam friends or ventrilo if you wanted to. Won't effect gameplay whatsoever.
In general I see stacking to a particular team based on map. Some maps, NF is consistently stacked, other maps, BE is consistently stacked. Hiding the scoreboard is using a band-aid to cure heart congestion.
Mootant: KM Plugin works on the KM server, all the servers don't run the KM plugin. Can't talk about KM likes we do when we talk about Mittoes confusing noobs about resources. Demented: Few maps people stack one side. I think infantry based maps are the only ones where people really like to pick one side. Avair: It could be a server side option.
Randomizing teams will not make them balanced. Yes, it will help a bit but to properly balance teams You need something more complex than just putting people in random teams. Please check this topic for a discussion on how this may be done. The first test session of the new plugin is meant to happen on saturday (tomorow), the hour is not set yet, it will be announced through SteamGroup events system.
