Musketeer -> Sniper or Musketeer -> Gunner, perhaps both Sniper and Gunner as jobs. Cannoneer or Fusilier would fit as well I suppose.

I just want an excuse to make a second character for Limsa Lominsa.

I do ponder if a gun class will be less kiting than the archer, more powerful/supportive but with "firing times" that are similar to what the magic classes currently use.