The idea behind this would be that there would be a limit to played (max of, say, 8, and that the more players, the more difficult) and have kits available. I will list off ideas for kits down below. Along with this, it could be possible to add multiple arenas with different themes with different mobs (nether map involving undead/blazes, graveyard involving only undead, an end map with endermites and enderman, etc.) and this could get keys and crates from completing certain maps. I would be up to work on maps if the server needs a build team put together.
Kit propositions: (All kits should have 3 drinkable health potions, unless otherwise stated)
Ninja: Diamond sword, 3 speed potions, leather armor
Knight: Iron sword, iron armor
Chemist (basically support): A mixture of splash potions (healing and damage), along with gold armor and an iron sword
Barbarian: Diamond axe, iron armor
Assassin: Leather armor, diamond sword, 3 strength potions
Feel free to add more ideas for kits or maps
~Jett