Like you can have Machinist have a sub-weapon and become a Corsair or Cannoneer

Astrologian with Geomancer

Warrior with Berserker

Black Mage with Magic Knight

Dragoon sharing skills with Machinist (Like Edgar from FF6, it was simply called Machinist though in that game)

Paladin having a DPS sub-job called Templar from FFT

So on, so on.

They would all share the same weaponskills, but some skills being exclusive.

I know its been talked about before, but its fun to think about what could have been.