MK3 and MK4 power armors (bigger grid, larger inventory), also adds various equipment (Night vision MK2, Energy shield MK3, Fusion battery, Singularity...)
Mods introducing new content into the game.
Armors or armor equipment.
Title says it all.
Well I didn't set a hard cap, so it's whatever you want I suppose, I wouldn't go overboard though, going too high is likely to cause issues.