If there was a 3rd branch for thief, bowman or pirate...

Pirates ARE thieves though... You'd have a better time arguing that Ninjas, despite being ROGUES are not THIEVES.

I would say Gunners should have been 3rd class for Archers, and the fisticuffers should have been 3rd class for Thieves. Archers are marksmen, so it would make sense for a person using a pistol to join their ranks, and a thief beating enemies with his "bare hands" wouldn't be outside the realm of logic either.

ps I don't think a ballista user would be any good... do you know how big that pomegranate is? Think of a siege catapult. Think of how big that is. Now imagine A pineappleING CROSSBOW THAT SIZE. That's what a ballista is.

I know.
Imagine a Scorpion- for 2nd Job
A more mobile faster Scorpion for 3rd.
And a FULL OUT INSTA-FORT Ballista for 4th- With some crazy stationary DPS
Also Imagine an Awkward arcing super-Arrow Bomb for 2nd job to make sure you didn't just die.
And a Iron Arrow variant.
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Save booster for 3rd job though(mage style) since they do such heavy SLOW damage.
...
And A setup time for packing and unpacking would make sure that melee range was a total peach.
A very tactical and albeit limited class for training maps.
It would also be pretty good for luring if it had a mass damage/stun move.