Hi !
damnation, first post ever ^^
I just wanna say that this theory might be true, in fact i'm a french reader of Sanderson (so sorry for my english btw). And in the french version of mistborn (fils des brumes) Spook is called..."spectre".
And the ghostbloods are named..."Les Sang-de-spectres"
Spectre is a word which means ghost. So in french the link jump directly to the eye of the reader.
So...Spookbloods is maybe for real.