[hornet]

To me, it's still rather unclear what your asking.
Blocking the menus? Simply hook ShowMenu and VGUIMenu messages ( and filter for the correct values ) and block them.
Showing your own class menu? You can just show it after blocking the other menus.
Force team join? Just use engclient_cmd( "jointeam" .... ) .
And then you won't have to worry about jointeam used after that because it will be blocked.