I can see Beastmaster and Blue Mage branching off of the same base class. Weapon would be an axe and Beastmaster charms creatures while Blue Mage learns their abilities.
Was thinking this the other day. Class is Animist - mimicing the monster abilities. BST job focused on synergy with the animal spirit, as kindred. Requires ACH sub (wildeness ranger-type aspect, I guess). Gets charm (short-term effect, but doesn't turn mob hostile when it ends), tame (beast cc), and maybe 3 different pets that can be "called" - tank, DPS & healing -> support/DPS role, filling gaps as needed. BLU job is about forcibly taking an animal's "soul," sort of a light/dark duality of the animal focus. Requires THM sub (more magey, plus darker focus). Abilities are tougher to fit into 5 slots, though. Only way I can see it working is each ability quest leads you to defeat a certain instanced "NM," but one that can be soloed. You have a technique to steal it's soul upon death, learning an ability (kinda similar to the Sith Inquisitor Chapter 2 storyline for SWtOR), giving you 5 BLU spells @ 50.
The only issue I can see, especially if you level BST to 50 (giving you an instant BLU 50), is that how do you explain how you came to learn these abilities? I guess we'll find out with SCH/SMN, but it may be that if you level SCH to 50, you have a SMN 50 BUT
you still have to go through the 5 job quests to learn the SMN abilities. Makes sense, at least from a thematic perspective. Plus it gives you a chance to get a grip on the job-specific abilities too.