The point of the coliseum is to have knights fight against each other for crowds of monsters.

I do like the base idea though. What could happen instead would be a 4:1 ratio for teams, then have one team with some sort of contact damage (the ghosts) and one team which can pick up the heat on the ground (pacman). The team that can pick up heat is dressed up in regal-themed proto gear, and the team that plays as the ghosts are put into random kat costumes (kat armors in full).

When a "power heat" thing is picked up, all ghosts get changed to the blue personal color and are stunned and lose their contact damage for about 10 seconds. During this time the pacman team can instantly kill all ghosts that touch them.
The kat team will have a base of MSI: Medium whereas the pacman player will have an MSI of low. This means a kat can catch up the to pacman. The pacman team can dodge however, and the kat team cannot. This means the kat team must work together, but at the same time the pacman has the ability to avoid them and their increased MSI (this means that the pacman can dodge through kat players. However, if two kat players are moving with space between them, the pacman becomes trapped).

The game requires 5 players to start, and maximizes at either 10 or 15. There are no weapon particles going on so we might be able to make the 15 work no problem.
The first player is assigned to team pacman. The next 4 are assigned to team ghost. The next player is pacman, the next 4 is ghost. This means you could have 2 pacmen and 4 ghosts, or 2 pacmen and 8 ghosts. Perhaps a better scale could work.

Both teams can respawn, however there are 12 second "pulses" (6 seconds with 2 or more pacmen) to whenever a ghost can leave the kat spawn room. This means if all ghosts (4) are defeated by the pacman, they would need 48 seconds to completely respawn. In the meantime they can throw pots out of the spawn room and try to hit the pacman, stunning them. Team pacman would lose a substantial amount of points every time they are defeated. Whenever a pacman is defeated, they lose 75% of the heat they've earned*. 75% of the lost heat is either spewed out where the player died, or randomly thrown across the map so that the player must collect the heat again. This means that if a player is constantly dying to the kats, they will eventually lose total heat and be unable to win (explained in next paragraph).

*if the pacmen hit has less than 5% of the heat on the map total, they are defeated, unable to respawn, and the heat on them is lost for the entire time. You know, to make AFKers punished for not playing the game.

For the pacmen to win, they must collect and maintain 60% of the heat on the map. For the kats to win, they must prevent the pacman team from keeping that much heat. If the pacmen collect 100% of the heat the 1 minute countdown timer appears and the kats have 1 minute to get the pacman team below 40% heat and keep it that way until the timer runs out. This means if the pacmen team get 100% heat then they can still win if they have 50% heat after 1 minute, whereas they would lose the game if they hadn't gotten 100% prior.

These changes make the game PvP, unique (like blast network is unique), and not be in any way Pay to win. You'll have some latency issues like blast network does, but since it's about knight-to-knight contact you'll always see death approaching before being hit by it.