Oho! I don't know about Corrupted Wild Shape, but that Tainted Druid feat could be interesting, particularly for RHOD. I shall have to give that more thought...
For my own (or at least Glyphstone's contribution, coming from the RHOD Handbook): try lich-ifying Druid 5/Ur-Priest X. Seventh level spells by level 12 ought to impress someone ;)