I had an idea for Sacred Shield that could implemented specifically for Ret. The whole point of the way I conceived it is to create more dynamic play between Rets' personal survivability, group utility, and damage.
Sacred Shield (WOTLK model): Is now baseline for Retribution spec. Cost: 1-3 Holy Power.
Protects the target with a shield of Holy Light for 10 seconds, per charge of Holy Power used. Absorbs X damage based on spell power. Can be cast on multiple targets. If cast on self, you cast a Shield that is half as powerful as when cast on others, all other instances of Sacred Shield end, and you deal X% less damage. If cast on others, all instances of Sacred Shield on self end and you deal 3% less damage per instance of Sacred Shield.
My proposal is this: Remove Inquisition, and replace it with this hypothetical incarnation of Sacred Shield in its place. Give us increased utility via Sacred Shield and the choice to decrease damage output levels similar to the decreased amount of damage that we currently have if we're not keeping Inquisition up. The trade-off is we no longer have to worry about Inquisition consuming resources, and if we choose not to use our new Utility spell, then we still have that extra sustained damage from the hypothetical removal of Inquisition. This is also fills that survivability gap that Ret has at the moment, without being too Overpowered since we will take a hit on damage even when we cast it on ourselves. But the idea is that we would want to use this spell when the utility it provides is better than the damage trade-off, and if at any point it's not, then we can cancel the spell and gain our damage back.
The whole point was to stay true to Ret being a support class who can deal damage. As it stands it's very hard to find uses for Holy Power in its current incarnation simply because very important abilities like Inquisition, TV, and WoG are all competing for the same resources and for the same spot in our rotation (more so from a PVP perspective).
If you removed Inquisition from the equation, you could allow Ret the possibility of being able to use different spells strategically without worrying about having that Holy Power go to waste because you needed to cast it on something else instead (like Inquisition). The conditional effect of the spell requiring you to sacrifice damage output is in line with the original design goal of Inquisition existing more or less to limit our burst potential. It would end up being a very balanced approach to personal damage and utility.
I think it really captures the picture of a Paladin as a battle healer; someone who can protect their allies and dish out damage at the same time, or go full on support at the expense of dealing less damage. Being able to bubble your teammates would be a pretty cool and engaging way of providing support, not to mention the visual splendor of everyone running around shielded by your bubbles of the light (Of course they should probably still be able to be spell stolen and dispelled).