I see BLU/BST/PUP being similar types of limited jobs in that they involve a mini-game of sorts. BLU was defeating mobs and learning spells. BST could be charming/capturing mobs when their HP is low and fighting along-side them (and their each individual unique commands/skills/spells) to defeat things. PUP gather parts from defeating different kinds of mobs and using them as attachments for their Mammet. Different parts would have different effects and enable the Mammet different spells/traits/stats/or combat logic (melee vs healer). There would be a limit to the # of slots you could equip, similar to BLU spells. Each of these 3 limited jobs would have their own solo content (like Masked Carnivale) but balanced for their own unique style of combat.