Then I'm not really following the point of the discussion since a DRK would likely use a scythe or great sword anyway. THM uses staff, MAR uses great axe, GLA uses sword/shield.....weapon wise, there's not really a tie to DRK anywhere.
A couple things.
Dark Knights using single-handed swords is nothing new in the Final Fantasy-verse, and we know ARR is trying to pay a lot of homages to it. Cecil, who most people probably know as one of the most famous DRKs in the series, used a one-handed sword and shield as well. Just because Final Fantasy XI ushered in the idea of the scythe-wielding DRK doesn't mean it has to continue to be that way.
Additionally, consider that a class using multiple weapons is already ongoing in ARR, and was a thing back in 1.0 as well. Gladiators use both daggers and swords. Conjurers and Thaumaturges respectively have the options to either go two-handed staff, or to use a one-handed wand (with a shield in the offhand).
In other words, it stands to reason they could simply introduce Great Swords as a different type of weapon for GLDs or Marauders to use, and it wouldn't really be all too jarring.
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