dualist who believes that we have souls in addition to brains … then scanning your brain could never be sufficient

Funnily, quite an opposite :). Dualism, however implausible, could possibly make uploading identity problems more simple: if there are some properties of material objects which determine to which (if any) object a particular soul connects to, it could be possible to make a copy (or few copies) and has one of them get the same soul as was in the original — solving, along the way, the no-branching problem described above :)

Too bad, the world is not as simple as dualism would make it.