Something that would be useful for packs with a wide variety of mobs that spawn.

The ability to set a maximum number of a type of natural mob spawns that can exist in someones spawnable area.

For example limiting mutant bosses to 1 or so. or reducing zombies, creepers skellies etc from normal night/darkness spawns down to like 10-15 a piece so more unique things with lower weights can attempt spawns with the left over cap like quarks special underground undeads or dungeon gear's mobs.

Thanks for the feature request. While this wouldn't be that challenging to implement it is very out of scope for this mod. Bad Mobs is meant to be a simple mod that non-technical players can throw in to remove things they dislike from the game rather than being a complex pack tool that can be used to replace the vanilla spawning system.

I would recommend looking in to McJty's In Control mod which provides much deeper granularity in modifying mob spawning.

Ah yep. I figured this would be the case. Thanks anyways.