Thanks for all the advice, everyone. My background is in philosophy which is probably why I'm looking at this question a bit differently (or perhaps wrongly). Fwiw, philosophy programs aren't interested in the philosophy of history either, generally speaking.
I suppose this interest will have to remain in the background of whatever discipline I end up focusing on, unless I choose to do a more interdisciplinary program like some of you have suggested.
It's an interesting thing, these works on historical theory/historiography as done by working historians; they can seem to necessarily outlive the actual history done. For instance, (and I'm sure these answers change from discipline to discipline) which is more widely read: Carr's What is History? or his The Twenty Years' Crisis?