Imagine playing normal 4v4 but now each player has unique traits. Everyone still starts off equal but killing someone grants you a temporary ability for several seconds. For example, one spartan class can kill someone and charge their repulsor which they have like 3 seconds to use or they lose it.
This repulsor class also has an unique neutral equipment which they must fight for ammo on the map to use. Basically everyone is fighting for the same ammo for their own unique class equipment.
while the neutral equipment is neutral, it can also have slight advantages for each class. For example, the neutral equipment could be a bubble that slows down projectiles that lets the repulsor fire back easily.
The only extra thing that would be needed is some armor effects to distinguish each class when theyre powered up.