I know the penalty system for quitting ranked games with missing teammates is getting updated, but in addition to that, I think experimenting with increasing the respawn times of the team with the most players could be a good way to give the other team an opportunity to compete in the game.
I would love it if they took things even further.
Make the teams even. 3v3. And have the extra player rotate off the bench with each death.
I don’t view this as a bad suggestion honestly. Having it that it forces even teams even with more players, and it they wait till one of their teammates dies so that they can replace them. If it becomes a 4 vs 2, then only 2 players can play on the team with more players, and they wait in line to respawn. The first who was dead the longest will be the first one that respawns when one of their teammate dies.