There is lots of ways this could be accomplished - a talent like Beacon of Light that you placed on a target that directly converted the damage the Paladin would deal into AoE healing, perhaps about wow gold, or a beefed up Judgments of Light that stacked with the Paladins attacks to provide really significant group healing but which required the Paladin to keep attacking to keep the stack up.

There could be a specific Holy Paladin Aura that provided a small but noticeable group heal or even a Heal over Time effect on a designated target where the damage the Paladin deals creates healing on those with that specific blessing to get wow gold. You had have to watch how the numbers work: either the Blessing provides a fraction of the Paladins DPS or the Paladins damage is instead converted to healing, so that while he or she has to stay in melee range she is still providing healing and not actual damage to the group or raid to get wow gold.

This is just one path, of course, and I have neither the skill nor the resources of the entire Blizzard dev team who can come at this problem from all sorts of angles I am aware I am missing. Still, however they decide to solve the issue of spell power plate on a tanking class in PvP and the unexpected healing power it gives about wow gold, I would really like to lobby for the complete and total annihilation of all spell power plate. Destroy!