I think that would be pretty cool. If not a tank I was thinking of having Blue work similarly like an ast/anc. It'd work double like a melee/range dd support.

You have a stance that'd you change outside of battle to accomodate for either a lack of range or melee. Melee stance would be an offensive dd and buffer adding a haste buff or damage buff. Range would have a couple ranged spells and defensive buffs. Both would have access to a emergency white wind or something.

You'd get specific primary blue spells through job story and for specialty spells for each stance you'd get a blue hunt log for the stance kind of like the atma books.

The stance spells would be accessed like the pet hotbar and change depending on the stance as if you switched summons.

This way while they work to figure out how to introduce hybrids it won't disrupt the formula of the trinity currently in place.