Tempered Will could have Prevents Cast Interruptions added to it - the addition of job-specific spell casting abilities for PLD makes that seem appropriate.

PLD spells works separetely from their core - interrupts combos, delays the GCD cycle, etc etc. I think that added synergy between the GCD rotation and these spells would make them feel more integrated into their kit.

Just example: If Royal Authority had an added effect that gave a short duration (or a 1-and-done buff) Spell Speed boost to the PLD . Like, a lot of Spell Speed - enough to reduce the GCD for a spell by a significant amount. Would open up Stoneskin & Clemency as fourth hits in a RA combo.

In the right scenarios SS&Clem can do a lot, there's still the MP gate PLDs need to bypass, so adding a bridge that links their GCD core to Spells could make that flavor less penalizing.

I would still trade Divine Veil for War Drum or Phalanx.