Survival Mode Tweak

I've come up with a tweak to what I'll call "Survival Mode" in this post. Survival Mode, for our purposes, is a mode in a video game (usually a first person shooter) where each team (usually 2, possibly more) has a certain number of lives, and the first team to run out of lives loses. (Problems arise with 3 or more teams. Does the game end when 1 team is out? (presumably, whoever has the most lives left wins) Or do you keep going until there's one team left with lives? (creating a player elimination - or in this case, team eliminatiion - mechanic))
But what if the teams have different numbers of players? For instance, what happens in a 5v4 game? Well, usually, each team gets the same number of lives. In some games, though, the larger team might have an advantage, as 5 people are better at killing 4 people than 4 people are at killing 5 people, all things being equal. Here, I propose a tweak to this sort of gameplay.
Instead of counting deaths, count spawns. In this way, the team with 5 players uses up 5 spawns right away, while that with 4 players only uses up 4 spawns. Of course, this shortens the game unless the base level of "lives" is changed, but that's up to each game, anyway.