One of the main reasons for avoiding duplicate weapon types is that it makes unique weapon design and job identity more difficult, which is enough of a problem with six different sword variants as it is. Half the time the 'Greatswords' in this game are being redesigned as oversized cutlasses to avoid overlapping with some very similar albeit downsized PLD swords and NIN daggers.

If you want to avoid ending up as Pirate Strife, you're better off looking into more unique weapon designs. A better alternative is to look at the likes of FFVII Advent Children's Fusion Sword or better yet, FFXV's Armiger. In the case of the latter, you'd effectively be fabricating weapons from the air, and each Weaponskill could very well be a different weapon type. A variant of this type of fighting style could be something similar to Xenogears' Esmerelda, where you have a job that situationally transforms limbs into weapons while fighting. I'm not sure what the current lore situation is on BST post-Bozja, but that's one way of implementing it as a partial shape-shifter. Perhaps give them a bell.

Mystic Knight is a very popular choice, but doesn't fit with the SOLDIER aesthetic. I would have expected something either Thavnarian or Corvosi in design. If you want to distinguish them from all of the other sword-wielding gish jobs, you could give them a whip or flail instead, and let their casting have more of an elemental buff/debuff focus, in place of the standard magic-as-damage routine.

That being said, I do think that it will be some time before we see more melee jobs. Could we have a blitzball-wielding physical ranged? A Void Mage that uses Lulu style dolls mixed with curses and DoTs? What about a melee-range healer that uses a pole or quarterstaff, and generates and mixes proximity aura effects by smashing potions? Could you design a tank that uses Ward's Anchor or Nero's Hammer? Swords are only the tip of the iceberg.