Artificers have two spells/infusions that allow them to add their intelligence bonus to their attack or damage rolls with a weapon. However, casting one of these spells on the same weapon dispells the other and replaces it.

I suggest that paladins get something similar. "Divine Might" would allow the paladin to add their charisma bonus to damage rolls, while "Divine Shield" would add the same to their AC. In other games, these were feats, but in DDO it's entirely possible for these two to be spells or enhancements.