I agree with the general idea of removing or revamping the tanking stances. Consider the AST stance, they make real differences. Now the best would obviously to build the tank jobs with good stance mechanisms, but failing that I wouldn't mind just removing stances.

For example Shield Oath could add damage reflection per hit/block/parry that is determined by the gauge value, and your crits proc a Shield Swipe and reset Shield Swipe recast time. Modifying the PLD combat to feel like you're a master of the shield. Sword oath could be a skillspeed focus where each block/parry give you a stack of skillspeed increase for 6 seconds and your auto-attack/weapon skill crits will make your next weapon skill crit.

Defiance could put up an 15m aura that reduces enemy's damage done by a percentage depending on your gauge value, and your crits on a target will cause splash damage to two other targets within 5m of the original target. Deliverance could be a crit focus where each crit gives you a stack of yet more crit for 6 seconds and at maximum stack your next weapon skill is guaranteed to crit but will clear the stack.

Grit could give all your weapon skills an HP drain component, and parry/dodges automatically cause riposte damage on the enemy and give you 100% HP back from the riposte damage. Darkside could give all your weapon skills an extra Darkside DoT effect on the target that will buff your damage and explode for a damage shield on you or something. And make Grit and Darkside mutually exclusive? I don't know, I actually don't exactly like how the DRK plays so I am really just making things up for the sake of having something for DRK now.