Or instead of joining a team, why aren't all the teams empty like every beginning of a game but you have to make them by yourself. A little bit like UHC back in days. Let's say you do /team create 8 (<- number of team, can't go higher than the normal possibilities) let's say ImABubblehead, DutchLemur, zDutchie and Mooofin. If you make a team all the players you mentioned in your command will be added to your team. The other persons who don't join a team will be added to a random team (just like it is now)
That seems like a decent idea. You have my support!