Promoting members gives them significant responsibilities. If they aren’t prepared for the role or don’t take it seriously, it could have adverse effects on your Team. Screen your members carefully and promote only those you know and trust.
For example, Vice Captains can kick almost anybody in the Team. Assistants can kick out members. This leaves a lot of room for dirty politics if handled improperly.
Kicking people for no reason might be a mean thing to do, but it’s not against the rules. So, preventing it is up to you!
We can’t retroactively change Team dynamics in the event of one bad apple. We like each Team to be pretty much independent.