While corsair seems obviously in theme, I wouldn't be 100% certain since, if they really wanted to rub in a distinctly pirate melee weapon, it wouldn't be a small straight sword like we see, but a curved sword like a scimitar, saber, cutlass.

Straight sword would be too indistinct from paladin's weapon, dual blades while on scouting gear would be too similar to ninja. Then again, we do already have white mage and black mage rods/staves/canes and scholar/summoner books

All my money is on green mage DoT/support caster. Even though they have distanced themselves from DoTs, I think they will implement the concept of DoTs in an indirect way that's more in line with its current philosophy of mechanics, sort of like how reaper channels its void avatar without it being overtly a pet entity, and the current summoner (other than carbuncle who continues to be an annoying vestigial crutch).

The way green mage can do nature DoTs without just being like Bio/Venomous Bite: apply stacking debuff on the enemy that you choose when to detonate like Bane, dealing more damage the more stacks were applied. This way (early detonating), burst damage can also be done with the "DoT" gameplay, and also work on enemies that die quicker than the debuff duration, and doing something other than just waiting for ticks alone to whittle its HP down. Poison mechanics are being phased out because they are not interactive or mechanically interesting, plus technical server stuff, so you just have to make it interactive and engaging to maintain these debuffs, and decouple it from server jank like they successfully did with machinist's Hypercharge and ninja's mudras.