this is an MMORPG while some unimaginary types might frown upon those who RP ingame there are still plenty who do it there are those who even eRP ingame so just do your thing and have fun

i would say machinist is probably best for playing a pirate, they get to use pistols and they also get to equip the level 50 kirimu outfit which makes you look like a pirate (the revolver of the wanderer weapon goes nicely with that outfit although the weapon has to be unlock via wolf marks)