It would be a challenge, but....
It would be easier if you worked at the very end of the leg rather than stepped down or within the bevel. That way you can saw a flat on the bevel and work in from the end for the mortise. Tenons would be the same as normally made.
If it were me, I'd use a bandsaw to saw the flat and make the tenons and a dado set with a jig to hold the piece on the table saw. It wouldn't take much hand chiselling that way... just me.
I do like the idea, and I've seen it somewhere but couldn't find an image either. :frown2:
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)