I've already made a Hunter class that covers most of the differences. Anything beyond the class' admittedly slightly bland scope can be covered with multiclassing. Can post it if desired.

I wouldn't have put these monsters together. The Shapeshifters [were there two or three?] were specifically stated to have been born "human" before their mutation became evident.

The Siren, Changeling, Wraith and possibly the Crocotta [Long Distance Call, S3, E14] all seem to be a distinct species or genus. The first two don't even seem to be shapechangers so much as some kind of sympathetic illusionists, given the way that they are visible in mirrors.