Lore wise, I do picture Beastmaster as someone who trains beasts for the purpose of protection, not for offense, conversely to how Lyon and Pagaga worked in Bozja.
There is room in the lore, too, for Lyon to return in their questlines, if you've read all of his field notes. Certainly, at least, we could do a lot with it.

I'm a bit mixed on what level would be best to start Beastmaster off. on one hand, making them start at level 80 in a new expansion would be good for the most part, but it would make a lot of sense for them to start early, as you could start 'training' with your Beasts from early on, and it could be something available early on for newbies. but that's another discussion.

My hope is that this concept seems fun to others, too. Of course there's room for improvement and balancing, but as a general overview, it works well.

If you liked this, I do also have a couple other job concepts over on the DPS forums! I've made a Green Mage as a hybrid melee/caster, Ranger as a melee with a crossbow off-hand, Sword Saint, and a Time Mage, but Beastmaster's definitely has the most stuff to it.

Let me know if you have any thoughts on this! There's always ways to improve on a concept, especially with fresh pairs of eyes. And if people have particular Beasts they'd like to have included, I'd love to see what folks would come up with for how they would fight!