If it was Garlean related I could see the following. Oracle(Support) and some Mech Based(Tank) and maybe if they also added a DPS, Gunblade(DPS)
Basically the Oracle Support would relate to the Garlean's third eye in which certain but a rare small group of Garlean's capable of casting magic are able to use the power of their third eye to empower said magic. Or if we were to take spacial recognition to mean the aether around them, maybe they could predict the currents of aether to reproduce magic even though they aren't technically casting magic. As an Oracle they use their spacial recognition to predict the currents of aether to predict magick and not "cast" but allow the reaction of magic to occur by being able to properly predict the situation needed to execute said currents into a magical effect. Tool for Oracle could be Talisman and even dive a bit deeper into Garlean lore since religion I believe is banned, they could be seen as a small resistance group that wish to keep the practice of their faith and through it have found a way to control aether.
For Mech Based, it would be like a power suit inspired by magitek armor, the next stage in technological advancement that allows for more mobility compared to current magitek armor. Mainly designed to combat against the magical threat within Eorzea the mechanic would involve an "Aether Feedback" that is charged up when tanking and even an attachment that allows the armor to gather aether around it in an attempt to disrupt the power of Primals that may use the environment around them to gather aether. For their tool I"m not sure what I"d go with maybe a Power Armor that is worn on the chest and their battle stance activates the armor for combat purposes.
As for Gunblade, I really don't know how I"d turn this into a job since I do feel in design it could be to close to looking like Machinist or Red Mage. I say Machinist because of a potential bullet mechanic and I say Red Mage because of their style of using magic and melee, front line and back line mechanics. It could be pure TP based so the magic range aspect wouldn't be there, it could still have the same idea of going back and forth between close range and long range but I do feel it would just look to much like the above two jobs mentioned. At most I can think of maybe "Trigger" the design of being able to combo your damage and make it more powerful, much like Renzokuken but even that sounds like it might be to similar to Samurai's current design.
But what about a "Blade Break" mechanic, granted this might be punishing for said job but the idea being you can trigger anytime and but you weaken the integrity of your blade, aether can be used to restore the durability of the blade, but when you "Blade Break" you can't use Trigger until it recovers. In a way the job could be designed to go fast, the ability "Trigger" would come up anytime a weaponskill is used during the 2 second global cooldown, so the Gunblade user would pretty much always be active Slash-Trigger-Double Slash-Trigger. . . where maybe Trigger is used beforehand to augment the next ability used in a combo but there is a limit to how many times you can Trigger, That could get messy though. I am honestly curious how others would implement a Gunblade like job cause I really do think it could be way to close to the design of Red Mage, Samurai and Machinist, unless mixing them all together into one job would be unique enough to be it's own job. Like the Trigger using Machinist Bullet, the Red Mage's front line/backline movement(but more focused on front line than backline where range actions require a certain distance in order to execute) and Samurai's combos that build up and allow access to other abilities, then maybe it could be it's own job. But I honestly am stumped by a design that would be unique holding no similarities to other jobs already in the game.