I wonder if something like this would be possible. like some way to force players that join to spawn as a mob directly. zombie creeper skeleton chicken wolf fox cow sheep pig ect. even if the player has never killed any mobs.
maybe spawn with a selection of mobs already unlocked somehow. some kind of mobs to choose from available option. with the ability to add or remove mobs in a config file. with a default chosen mob to spawn as? possibly limit mobs that can be morphed into?