First suggestion: Lives are shared instead of individual. Teams receive (x * t) - t lives (x = number of lives, t = number of players on your team, -t for the game to begin with 0 reserved lives if lives are set to 1). If you die, 1 life is removed from your team's counter. Once there are no reserved lives left, your team will no longer be able to respawn on death. Pros, everyone, including the worst players, get to play the game until there are no reserved lives left on their team, making the experience better for them and preventing them from no longer playing the game because they found it too hard/punishing. Good players will have an harder and more challenging time, giving everyone a better and more hardcore-like experience. Cons, trollers can troll the game by dying many times and removing all lives from their team. Some good players may find it fustrating to go down with their team.
Second suggestion: Remove team collision. The amount of times I've killed or got killed by my own teammates is insane. This would lead to teammates just helping each other by giving power-ups and attacking enemies instead of bothering each other. Pros, infinite. Cons, none.

