Depend on the variation of that sword still.
We actually do have one more type of Sword Job that is not used yet from the FF series in FF14 being the Spellblade Magic user sword job. This is the Mystic Knight job we all know in FF series.
One of the Iconic jobs in FF series involving the Job magically enhancing all their sword attacks with magic to perform melee range attacks such as Firaga Blade, Death Blade, Drain Blade, and etc for pure melee combat with a magic infused sword.
What sword they can use will still depend on SE developer's choice but Rune Blade is the iconic Magic two-handed sword type weapon which focus more on magic use over physical attacks due to infusing magic runes into the sword in fantasy theme stories so there is still this version of a two-handed sword weapon.
With the right design choices, the Rune Blade can become the weapon of choice for Mystic Knight Job.
that is expected in any fantasy theme games. I already commented a off-topic reason why this is so common in fantasy games already earlier about this kind of issue with being creative with new Jobs.
Swords are just far too iconic to a point that most fantasy theme games just can't establish jobs solid enough to be loved beyond Swords which I do blame the conditioning we all go through growing up with how almost majoirty of fantasy theme games, books, movies, shows, and etc we read and watch always give the Hero and Villain a Sword as their iconic weapon and tend to make the strongest weapon in these settings a Sword. The Sword job just becomes the most used/popular job in the game due to this conditioning.
Heck majority of FF games has their Main Character be a sword user and even the upcoming FF16 Main character is another sword user. Only FF9 had the main character not a sword user being Zidane who use dagger weapons. Every other FF game has their Main Character use a Job with a certain variation of a Sword weapon. The Derplander actually started out with the Gladiator class during the FF14 1.0 cinematic (he switch to archer in the echo vision but outside of the vision he was a Gladiator as seen by his Tank gear and sword behind his back when he set out on his adventure with his two companions).
on a personal level, I prefer a more assassin style character as long it fits the bill of a assassin but Assassin theme jobs tend to fall under Daggers or sword style weapons which are both taken already unless they try for a special variation of these weapons. Ninja sadly did not in FF14 as each expansion update it started moving aware from its Assassin theme skills it started with as a Rogue to focus more on being pure Ninja with the job replacing all Assassin Job related skills to Ninja Job theme skills. Atleast with this shift, it opens room for them to make a actual dedicated Assassin Job though uncertain what kind of weapon they may choose.