I've always thought Rabican would be a natural Shade, considering he was killed by the Watcher. And we all know what the Watcher does to Avatara bodies he's just dispatched.
It's kind of far-fetched to imagine the Watcher not Shadifying the body of Rabican.
Although you've probably seen these already; in case you didn't know you can use the unused Myth II shade names of:
Nym
Sycorax
Gullveig
Cailleac Bheur
I understand you aren't necessarily looking for Bungie™ names but those are up for grabs. Also there is Turquine, mentioned in one of the flavor texts. I'd be cool to see someone's interpretation of one of these guys' stories.
-Welly