This is just an idea to balance out class concepts that might seem interesting but a bit overpowered. Making certain class categories where within a given team only a few people can play them, or only one per team, at a time would allow gameplay to be spiced up in ways that might otherwise ruin it if everyone could spawn as that class. You could also set these options to be adjustable for certain maps and gamemodes. So like if you create a Tank class that moves incredibly slowly has an absurd amount of health and a very slow firing but very powerful cannon, meant to only be used one at a time in a team, you can set up Free For All games to not allow that class. Or if we have an Engineer class that can construct useful things in the map like health stations, ammo stations, turrets, barriers, etc you can set that to only be available in two-team game modes and only allow one per team. This also makes certain enemy players high priority targets for enemy recons to try to assassinate.