Some mobs are not present for premiums that really don't have a gamebreaking reason not to be added, so this is just a list of the mobs that could be enabled for premiums: parrot llama evoker shulker* vex vindicator illusioner *with the shulker, the only downside is that player can disguise as boxes. However, the recent removal of the "SetSneaking" option, there will always be a name tag visible for players to see. Yes these are only 1.12 mobs. Yes 1.13 mobs exist. No the server is not on 1.13, so suggesting them is not the point of the thread.
Bumping again. It's been a while, but I haven't seen any reason not to implement these minor changes. It gives more animals to disguise as, making the premium and supremium ranks more desirable.