Perhaps if we had mechanics for Oaths that induce power.I like the cleric being more of a militant divine character, so I see it distinct from a mage. Priests give sermons in their temples... clerics venture forth and bash undead with martial might and divine rage. Traditionally, clerics have always been either front line combatants or a good back up for when the fighter needs to pull back.
In fact, I consider Paladins unnecessary.
The oath bound hero has legend and myth surrounding it the oaths are not necessarily very D&D like in many cases ... For example Sampson (symbolic divine oath about hygiene), Cu Cuhlaine (totemic oath opposed by social oath), Lancelot (oath to king and queen but also something about never being defeated as long as he fights on the side of righteousness in conflict with his desire to be challenged) now only one of them are associated with Knight in shining armor but.
A fighter or anyone really could then accept an Oath which then empowers him like an enchantment. It was considered a Fighter subclass all the way back.