Guild Wars 2

- Players can freely join and leave a team before a match starts
- Once a match has started, active players are charged a fee (let’s say 50 silver) when reverting back to spectation mode, or when leaving a match entirely
- Spectators are not charged to leave a match
- Active players are not charged to leave a match once a team has won

This will encourage players to commit to a game and to a team once chosen.

To avoid abuse by unwilling players going AFK during a match, team members can vote to have a player kicked.

Apparently you are referring to practice matches, those I don’t see problem in people “exploiting” the autobalance.
If you want a stable 5v5 fights but don’t want the pressure of risking the rank of the team mates, play unranked and be happy.