Blessing of Kings is great. It's a simple 10% buff to all stats that everyone benefits from. Blessing of Might is supposed to be good for melee classes (and hunters), but a warrior's Battle Shout can overwrite it. This happens all the time if the blessing is done by a paladin not talented for the improved Blessing of Might. Blessing of Wisdom used to have the same problem when used in conjunction with Mana Spring Totem until patch 3.1.2. Blessing of Wisdom would be ideal for mana users, especially healers. Even with change to keep it from being overwritten, it seems more practical to use Blessing of Kings over Wisdom when the totem can provide extra mp5, anyway. Plus, many mana dependent classes have talents and gear that gives them good mana regeneration. Plus, it's a pain in the ass to use up all those symbol of kings on a raid when those dirty druids, mages, and priests get to use only one reagent to buff the whole raid.
So, with all that seemingly unnecessary set up, here's my idea on how to change Blessing of Kings into something that makes all the Blessings usable in a group/raid.
Get Rid of Blessing of Kings
The stat bonus can be rolled into the two other blessings and allow Blessing of Sanctuary to be cast by all paladins. Blessing of Sanctuary already gives an extra 10% strength and stamina in addition to damage reduction and mana regeneration (mana regen could also be rage regen for other classes). Blessing of Wisdom could give 10% to intellect and spirit while Blessing of Might would give 10% to strength and agility. All in addition to what they already do.
This way everyone gets what they want and Blessing of Wisdom and Blessing of Might are no longer bastard children ignored in my spell book.