My thoughts on a few things that could help PLD:

Give PLD a reason to use / manage MP
This could help make the PLD a better OT while simultaneously helping with TP issues. For example, what if clemency gave a small damage buff to the target party member:
* The dps increase could more than make up for the dps loss of casting
* PLD isnt using TP while casting
* OTing lets PLD use MP restoration combos more frequently.

Rework Block
PLD is the only one really using the block mechanic. There is opportunity here. My suggestion would be that a successful block gives vulnerability up to the target who was blocked, which does 2 things:
* Increases PLDs MT party contribution vs physical
* Increases the PLDs AoE damage contribution (again vs physical)

An important thing to note about this is that the above benefits of a block rework exist while in or out of tank stance. PLD gets crap for poor AoE, but the lack of direct AoE damage is one of the things that makes PLD unique IMO: They get such horrible returns on Sword Oath in a large pull that it behooves them to use Shield Oath, and I dont think that is such a bad thing.