Added to your questions, what about the "Hogs of War" quote and the huge amount of destruction during Stephen's death, which to me indicate no "mere mortal" could have done this (i.e.: humans, Dwarves)? Trolls and Magicians might be able to do this, but I still don't discount the Hogfather, or a God interfering on behalf of a priest.
Magicians are most likely, IMO. Partly because we've already seen at least one magician. Partly because of what we've seen in the open: Sally (Stephen), Otto (Yuna), the Bursar (rana) and a Watchman (FT) all indicate "normal characters", and with only 8 other players left, a "supernatural" character feels out of place, IMO.

And the more I think about what Praz says about his objectives and how they align with FT's, without actually being in the Watch, the less sense it makes.

And that zombie: what use was the ladle? And the bottle? Did it have any meaning?