Be a bard or a paladin. You just need to strip the flavor.
Paladin = noble knight. They're honorable, chivalrous, all that rot. They get edicts from their king that allow them to perform miracles on his behalf (kings of legends had powers to remove disease, cure illness, and smite evil...think of Aragorn's "noble" powers....). You may want to shift a few minor details...such as change smite to Chaotic instead of Evil (for those who violate your Lord), but it's not absolute. You may want to loosen alignment requirements and the code of conduct, too, but you probably want to keep *something* in there.
Bard = noble courtesan. They're persuasive, charismatic, excelent at oratory, and also trained in some martial abilities. They 'use magic' by virtue of courtly trianing as well, and their magic often includes a vow, a speech, or a command. They gain power from authority itself. You almost definately want to alter the alingment requirements, but otherwise it works fine.
Don't be so quick to say that paladin = paladin, and bard = bard, and they can't be anything else. Using those abilities with some minor tweaks is much easier than dredging up a whole new class that's not integrated with anything else.