There's two MAJOR problems with adding Beastmaster.

1) Limited Jobs were a mistake and adding more just detracts from adding content you could play and enjoy as the normal classes. They'd remove Blue Mage or just rework it into a normal job if the community wouldn't hound them over it (and they should probably

2) The pet AI in this game is still trash and having a job that focuses on commanding beasts would play incredibly bad. Endwalker has already added systems like Island Sanctuary which clearly show where the technical limitations of XIV are, adding a job focused around AI pets would be so disastrously bad unless drastic improvements to the underlying technologies powering the game happened beforehand.