I think there's design space to keep it within Warlock without needing to create a new class. The power-dynamic aspect of Warlock's source of power, when viewed through the right lens, can be seen as pure lore/fluff. The old Shaman 2e class is a really bad example of the concept. You could go the animism/College of Spirits Bard route, but I'd like to see abstracted further than straight-up animism, and without the jack-of-all-trades aspect that comes with a Bard.
I'm working on a Pact of the Host subclass, but holding off until we see how the Summoning spells turn out for 5.5, which may affect my design significantly.