I've found another plugins that allow ranked players to disguise as other mobs and entities. It's been a while since we've had a disguise plugin because the old plugin wasn't being updated properly. I've re-done permissions, so it's likely they'll be different than before. Disguises can be used from Neon rank and up. To simplify things, if you have permission to disguise as a certain mob, you should also have access to any available sub-types for that mob, aside for a few exceptions like the giant slime/magma cube. Here's a run down of how the permissions are set up currently (unless I change something later):
Neon: Bat, Chicken, Cow, Donkey, Horse, Llama, Mule, Mushroom Cow, Ocelot, Pig, Sheep, Snowman, Squid, Wolf
Steel: Cave Spider, Creeper, Husk, Pig Zombie, Husk, Pig Zombie, Polar Bear, Rabbit, Silverfish, Skeleton, Slime, Spider, Stray, Villager, Witch, Zombie
Platinum: Blaze, Enderman, Evoker, Guardian, Iron Golem, Magma Cube, Vindicator
Carbon: Shulker, Skeletal Horse, Undead Horse, Vex, Wither Skeleton, Zombie Villager, Armor Stand, Falling Block
As before, disguises can be applied with the command /d, and un-disguised with /ud
Additionally, there's a helper plugin that adds an interface that hopefully makes the more complex mechanics of the plugin easier to use. To use the menu instead, use /ig.