If They Need Class Inspiration...

[Enkidoh]

There some characters even in FFXIV they can base new jobs on. Raubahn, back when he had two arms and his ability to generate flames from his swords and Meryweb and her dual pistols.

Have Raubahn's fighting style be something he learned back in Ala Mhigo as a traditional fighting style of his people back when they were mostly mercenaries and cut throats for hire and he decides to pass this fighring style onto us.

And Meryweb's style is something she picked up from her father, since he was the original owner of both her guns. And so we could directly learn from her and she eventually gives us a replica of her own pistols after we master her fighting style.

This is a misconception, Raubahn may have had two swords, but he never to my knowledge actually dual wielded them, the few times we saw him fight (such as the cutscene of his famous Colleseum fight that earned his freedom and his place on the Syndicate) he wielded a single blade while parrying strikes with a buckler on his left arm, just like any regular GLA. Raubahn is just a regular GLA, albeit one with his own unique attacks. (And besides, he ended up giving one of his swords to Pipin anyway, who wields Tizona like a great sword, but then, he is a lalafell so it's expected. )

Merlwyb's class also was always meant to be added since 1.0 (Musketeer, or MSK for short) - it even has a Guildhall in the Coral Tower (which the MRD's Guild ended up taking over) but it was never implimented and whatever SE had been designed for it probably was used for MCH instead, so that airship has long since departed (my suspicion for MSK's no show in 1.0 was due to how 1.0 played - back then ranged classes like ARC/BRD required ammo to be equipped that had to be crafted, like in FFXI, and with ARCs' already complaining about the high cost of making arrows, having to make bullets for MSK would have been too much, and so it was put asided and just quietly dropped and forgotten about, even in ARR when things were changed and ammo was no longer needed to be equipped, with ARC/BRD's arrows just... handwaved away).

MCH's guns are actually superior to the obsolete relics the Limsans use anyway, given MCH makes bullets from the user's own aether, allowing for rapid fire and automatic loading, where as the Limsans like Merlwyb are stuck with single-shot muzzle loading flintlocks that fire balls not bullets (the quest to unlock MCH actually rubs the technological disparity in the Limsans' faces, where Joye gleefully blows Rostnsthal's flintlock out of his hand with an aetheric bullet from her automatic rifle before he can even pull the trigger, basically showing how utterly technologically outclassed Limsa really is). So that's another nail in MSK's coffin sadly.