Weeeelll, I wouldnt say /nothing/ gets along with Outsiders, just 99.998% of everything would rather not. I would say that sufficiently solitary powers (ie not tied to a particular pantheon/power structure) could get away with it (random spirit of Prophesy being a good one), as could several sufficiently Chaotic powers (that might find a change of management for the Universe to be an interesting idea). And then there are any of a number of nicely pure evil villains from various mythologies that could reasonably work with them out of standard megalomaniacal arrogance and spite for their enemies. Hell, Ive seen a fairly convincing argument that the Fomor /are/ working with Outsiders, through a mutual link to Cowl (assuming the Fomor alliance hasnt been an outsider plan from the onset).
As a general rule, rather than outsider specific, Id suggest classifying any instances of multiple sponsors one of three ways, and just decide one is the default behaviour absent other specifics:
-Compatible: They augment each other in some fashion, either from a shared origin (saint sponsor becomes Archangel sponsor, Minor Greek Spirit to Primary Olympian, etc) or else compatable characterization (ie Angels and Winter could both be called Protectors of Humanity, for example).
-Unrelated: They are treated as separate in all ways, neither augmenting nor inpairing each other under normal circumstances. One sponsor for prophetic stuff might have nothing to do with another for Fire evocation, for example.
-Antagonistic: The Sponsors/granted themes are actively antagonistic, and will go beyond not operating together to actually imposing penalties. Holding both Fae Knight mantles has been compared to an antimatter explosion, for example. Having a Fallen granting Hellfire might prevent sponsorship from teh Loyal side, opposing elements mgiht not get along, old Diety grudges can always complicate things, etc.
In general Id default to the middle ground unless I had a driving story reason to lean one way or the other. Offering Augments for Compatible sponsors seems somehow redundant at elast on it's face, but at the very least is potent stunt fodder. Similarly Id avoid calling anythign activly antagonistic unless I really had to. Summer/Winter and Heaven/Hell are the obvious ones, and opposing elements would always makes some sense. But I could see inter-pantheon rivalries playing a role (maybe that Norse Fire Giant hates the idea of you getting otehr Fire help from Greek sources), and in a number of cases I could see pairs that outwardly should work but could be said to in the right circumstance or from the right perspective.
