PLD already requires more than straight tanking to keep hate. It doesn't need it to be even more difficult when compared to WAR. I feel sorry for the controller users out there(if there are any when on a PLD).
Shield Blocking is already hard to pull off without abilities and the damage reduction isn't that great either. I also think Aegis Boon is fine and doesn't need to be another type of outmaneuver. PLD doesn't need a complete rework, just more tweaks.
People don't bring 2 WHMS because of the hate on Cure. A WAR laughs at almost everybody on the battlefield that thinks they can pull hate from him/her. Only PLD have the hate controlling issues when compared. Even that BLM using his mighty combos isn't as much of a problem with a WAR Tank.
So in other words, I think what you suggest will create more problems, without fixing much, and still leave us Tanks(that would prefer to tank as a PLD) behind the WARs overall.