Totally forgot they could use guns. They had a very unique role in that game though and didn't make another appearance so they could really be anything I guess.
What they did have was essentially Attack up buff, Attack down debuff, Magic attack up buff, Magic attack down debuff, Stall (delays attacks, perhaps changed to slow or stun), a sleep, a gil boosting move, Berserk, Doom and a charming ability.
I can't see how their charming ability would fit in XIV and if they bring in Beastmaster it would cause a riot. Berserk is already Warriors. Doom has no place for players unless it's an ability that is placed on the mob does damage when it wears off. Gil boosting would be unfair to other jobs especially if they add in Thief and give it to them.
So then what we're left with would be a Musketeer (likely DPS) with perhaps 2 variances:
30: Praise - Attack up on party member(s).
35: Preach - Magic Attack up on party member(s).
40: Intimidate - Attack down on foe(s).
45: Enlighten - Magic Attack down on foe(s).
50: Mimic Darlavon - Sleeps foe(s).
OR
30: Praise/Intimidate - Attack up on party member(s) or Attack down on foe(s). Effect depends on who is targeted.
35: Preach/Enlighten - Magic Attack up on party member(s) or Magic Attack down on foe(s). Effect depends on who is targeted.
40: Stall - Stun or a slow effect. Likely a stun.
45: Mimic Darlavon - Sleeps foe(s).
50: Condemn - Places a debuff on target for X amount of time. Damage is dealt when effect wears off.
Just my idea of how they'd probably bring in the job. Likely be much like BRD in this case. Would probably have to face a penalty when using their buffs/debuffs like BRD as well to prevent them from being too strong/in demand. Perhaps very high recast timers, MP cost or TP cost while at the same time being unable to receive their own buffs.