Since Jade prototyped her sprite with her dreamself and Bec, when she went godtier her sprite, due to its dreamself part, was merged with her, causing her to go Dogteir. I know it's sort of a joke (God and dog having the same letters), but if a player prototyped their sprite with their dreamself and something more ordinary (like the mangled harlequin doll), would it have a similar effect? What about a dreamself and another human/troll?

From the information we have so far yes, it would have a similar effect I suppose. If you prototyped your sprite with your dreamself and another person and you then died on your slab\bed, then your dreamself would godtier as an amalgam of those two people.