Concept for a Magic Melee DPS

[Archwizard]

x3 Astral = Excalibur (Holy)
x3 Umbral = some dark type WS.

On the one-hand, and at the risk of being accused of trying to make a Keyblader job again, "Ragnarok" has historically been used as the name of another holy sword opposite Excalibur throughout the FF series.
On the other, "Galatine" in Arthurian legend is a blade described as "the shadow to Excalibur's light".

However, I would also note that both Excalibur and Ragnarok have been used as weapon names for Zodiac weapons for the PLD and WAR, respectively.
As an alternative though, you could consider other weaponskills available from the FF series -- for instance, Agrias and Thunder God in Orbonne Monastery provide us with "Judgement", "Cleansing Strike", "Dusk/Shadowblade", all as good options.

Hammer would be wholly unique but 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 suppose there's enough broadness with the Spellblade's naming conventions that you could go with a (Spell/Rune/Mystic) Knight and avoid having to discuss why it doesn't use some kind of sword.
But then you would have to ignore half the historical skill names like "Liquid Steel" or "Thunder Blade" (as well as a few of the suffixes we've generated like "-stroke", "-shear", "-edge", etc) since they don't fit as well with a hammer, and probably just go with the generic "-strike" name for almost everything. Plus I think WAR has begun adopting hammers as alternative weapons, particularly now that Slashing/Blunt vulnerabilities are gone.

That being said, even if swords are "overdone" by some standards, it is worth pointing out that A) there are multiple styles of swordplay the world over, enough that various weapons classified as "swords" can look and be used completely differently (such as, say, the Khopesh versus the Schiavona), and B) only about half of the jobs with swords actually focus on swordplay and technique, versus just awkwardly slashing around.

Given the Middle Eastern-inspired appearance of the Spellblade in FF5, BD, and various side-entries, I would say the most appropriate weapon-type for them would be curved swords (which FF11 treated with enough distinction to make the purview purely of BLU), such as Scimitars, Falchions, Sabers, Shamshirs, Falx, Dao, Falcata, etc.

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.

Oh hey, same hat. 'Bout the only things different are that I swapped some of the effects around -- Fire to do DoTs, Lightning for AoE (chain damage), Ice for (resource) recovery and Water for raw damage (acting as an energy conductor).

I've also been toying with the alternative idea that each one of them adds an "En-" effect that only lasts for a specified number of Weaponskills (2-3, prob), and that some oGCDs would cheat the system by inheriting the En-effect but not consuming charges by virtue of not being Weaponskills. Gives you a reason to cycle between certain ones and maybe even ignore standard "comboing" mechanics used by other melee (and even RDM) in favor of cobbling together a rotation based on what En-effects you need right now.

First wave place DoT, second and third wave generate resources, fourth wave resource burst.

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.

But that's good though! Having multiple ideas on how to execute one theoretical job goes exactly towards the point, that such a job could be generated and be completely unique from any existing job.
"Might step on the toes of X you say? Okay, I'll just pick any of a hundred alternative directions." It's complete insanity to block a potentially limitless number of directions just because one competing job might get one or two more vaguely similar weaponskills an expansion.

Oh, and two more ideas:
One, Strike skills could potentially do mixed physical and magical damage, with the latter's damage being scalar to the damage dealt by the former. This not only opens avenues for multihitting attacks and effects, but would allow the magic damage to increase with any Physical damage bonuses while also allowing the Spellblade to inherit some magic bonuses as well (albeit not so many as a dedicated caster). Plus, imagine being able to critical/direct hit twice in one swing, which gives some interesting potential for burst damage.
Second -

Gap closer:
- Warp Strike: Throw an aetherial blade toward the enemy and teleport to it, dealing damage to the target; 30 sec CD
--> Improved Warp Strike: Allows the accumulation of charges on Warp Strike, allowing it to be used twice in succession
--> Link Strikes: Allows Warp Strike to be used on allied targets as well, restoring the target's HP and causing your next Warp Strike within 15 sec to critically hit

Instead of having a Link Strike heal the target, it heals you, like when Noctis Warps away from a combat situation to recover. That way while you would normally be at a disadvantage with Bloodbath, the fact that you can use it like Aetherial Manipulation and still recover most of that damage could put your personal burst healing higher than most without having to sacrifice as much.

Plus you could also add in variations on Runic for personal defense.