I hope, against all odds, that we get two Magitek classes in 5.0.
Give me Judge and Soldier.
Judge being a Hammer/Club/Gunhammer wielding tank. Their gimmick can be the ability to pass "laws" that have different effects depending on if they're in tank stance or DPS stance.
Soldier being a Gunblade wielding DPS. Let it be a DPS that shares armor with Dragoon and make it like an inverse of Red Mage, where they're more melee oriented, but have a big burst phase revolving around them creating distance and using some ranged attacks, before closing in for a big finisher.