The fact is, the Shaman tradition as described in the book is a little nebulous. But there's almost zero problem with converting the traditions from Street Magic directly. With the exception of a few issues of spirit types that don't exist yet, which can be easily fudged with some common sense. So Bigity, if you are going to allow other traditions (and really, why not?) then I think your rule makes some sense. But since the Shaman tradition as described in the book doesn't just restrict itself to animistic shamanic traditions, then I think your rule is a little heavy-handed.