Having the newest person switch is a good idea, especially for those times when a person switches from one of two even teams to make them uneven again. It'd be nice to see something like this for a change:
Major Camper joined Bravo. 6/6
Major Camper left game. 6/5
Major Camper joined Alpha. 7/5
Major Camper auto-transferred to Bravo. 6/6