Or a reflect stance, for BALANCE, would have a Magic Evasion Down as it's downside, like counter stance reduces defense.

Maybe this:

Resonant Field- Recast/duration3 mins, reflects 50% of magic damage taken to the caster, 50% of the time. Magic Evasion-25.

And it's counter-part(haha)

Fearless Stalwart- Recast/duration 3min: reduces physical damage taken by 25%, evasion-25. Shares same timer as Resonant Field.

2 defensive stances, with positives and negatives just like Hasso/Seigen.

Or to even further simplify you could make one that increases pdt while reducing mdt, and the other increase mdt while reducing pdt. It would require you to know your enemy well, but what PLD worth his salt doesn't already study his enemies? These as well would be able to be used full time and would or would not share a timer, depending on the intensity of the ability, as to preserve game balance.