Hammer would be wholly uniquebut I do think this game tends to stick with tried and true FF classes. so Mage hammer isn't really identifiable as one. In fact blunt weapons now that I think about it are probably the most underused in the final fantasy series.... Pretty much just viking and onion knight.
I would love to see a more distinct debuff job, Devs do seem loathe to properly allow debuffs tho sadly. So the classes unique style would be management of multiple different resources that enhanced play? This actually makes me think of insect glaive from Monster Hunter series. They have to maintain "nectar" collection from three different parts of a monsters body to charge up, but can remain charged as long as they maintain the gathering of each nectar. Head boosts attack, Body boosts defense (flinching) and legs and arms boosted maneuverability. Put em all together and you are ina super strong state.
We have many jobs that maintain some meter or buff, Greased Lightning as an example. But we dont really have any that have to maintain multiple status enhancing statuses at the same time. It would be cool to have a class designed with that in mind. Each part could enhance the kit, but downtime would force you to temporarily lose a certain part of the enhancements for a little while and you would have the freedom to choose which one for different circumstances. or make it so there are many things that could be maintained but only 3 could be up at any time.
The class could start out with forced cast bars on all skills
-Wind could grant swiftcast, making it extremely valuable for mechanics, but it doesn't actually add dmg, so dropping it briefly at times in favor of pure damage would be a gain.
-Earth could grant the ability to ignore positionals (dont let the class use true north then)
-Fire could add raw damage, but not so much that missed positionals or inability to swiftcast wouldn't be more damaging in certain moments.
-Lightning could grant dots in the kit extra damage so you always want to have lightning up right before re-applying dots, but not otherwise
-Water could offer a healing boon to self thus making it a less used recovery buff
-Ice could enhance AOE damage.
-Thus max damage would come with Fire Lightning and Ice up at the same time, but this would make weaving impossible and movement impossible thus the class has to sacrifice some of its boosts to operate at times.
-Each could be accessed as a finisher to a 3 step melee combo, Enfire, enIce etc. or Icestrike etc.
-So the class would have one 2 step melee combo each with cast times and positionals (back on the first one) then have the finisher attack in 6 variants also all have positionals for full dmg (not effect, effect should always be safe to activate)
-each granting an ability that is maintained for about 9-10 GCDs.
-Thus only three could be active at a time with some mild 4 overlap.
-Then give it an alternate aoe combo that still finishes with the same Ice strike skills.
Immediately Earth and Air become extremely important, because they allow oGCD weaving and enable positional movement. but not so necessary that during certain moments they couldn't drop air to do more dmg.
This class would be highly difficult to perfect tho with this design, and would be EXTREMELY fight dependent. Every prog would see them using Earth Air Fire, but then for fights without positionals earth would drop entirely, and as fights became more memorized thunder or ice might occasionally replace fire, and with even further skill a player could at certain moments go full YOLO with fire ice and Lightning active.
I realize this is definitely a different direction than your original design but it could be interesting. It would be fun to see some class synergy too such as granting wind refreshing a Caster's swiftcast or something, but that kinda utility is really hard to balance around unfortunately. This is kinda I guess my own random vision for a spell blade now. Man. It would be hard to perfect it. But man I like the idea of utilizing all 6 elements