[Chaos_Genie]

I don't know what it's called but it's a plugin that allows mobs to stack, so you have 23x Zombie, instead of 23 zombies spawned, and when you kill one, the number drops to 22x, etc etc. It helps prevent lag when people create big farms, and you can still nametag passive mobs so they don't stack and you can reproduce!

[Cil]

I believe this was suggested before, but I believe it just makes the game less vanilla, plus it would make it easier to fight mobs when multiple spawn,
Example:
With plugin:
Skeleton Spawner -> Only one skele shoots at you.
Without plugin:
Skeleton Spawner -> Ten million skeletons are shooting at you.
Also, it would affect trident drops.