I have started a saga with my brother and a couple friends. A new person was invited to join and wants to play a magus persuing immortality. He (the player) is fascinated by the idea of the Lich from The Other Game and it certaily seems do-able in ArM.
The magus he wants to play is not inherently evil (at least to start with) and an easy approach to take is to lead him through the alchemical mysteries and maybe astrology. However, I feel that the Greater Exilir lacks a certain flavor (heh, heh) and I'm looking onto ways to spice things up.
As a side note, I'm trying to do this without tapping into RoP:M, RoP:I, or Hedge Magic, Revised. All three of these books are embargoed in another saga so I lack familiarity with them.
The third edition Wizard's Grimoire had proceedures for obtaining Lichedom. That may be useful. Maye Mysteries? Living Ghost combined with a way to bind said ghost to a fabricated corpse?
The books you mentioned, why are they embargoed? Those are awesome books, and kind of point to what you need (Binding from Infernal or Transformed Being from Magic).
Automatons (the inner mystery) and bind the spirit (the inner mystery) would combine in a flavorful if creepy fashion. Make the vessel, make it your talisman, and bind your soul to it. Automatons have no restriction on the materials used to make them, so if you want a flesh and bone body, as a lich would have, make one.
Talk to your storyteller, perhaps he can release some specific pages from the forbidden tomes in regards to this information?
I'm not positive, but there might be something in the NPC "Ulpris" from 4th edition's "Medieval Tapestry." The way my storyguide ran this character, he was basically pursuing Lich-dom, and tried to use the body of my slain PC as his vessel! I can't tell you if there's anything in there, because I have vowed not to read this section of the book.
I would also propose that your PLAYER come up with his own theories on how to do this. This would mirror what the magus would do in his lab, anyway. This way you could both explore his research, together, in-game. You could take his ideas, then create a rough outline of adventures that get him there (with some false-starts, red-herrings, and dead lines of research thrown in.)
Good point on letting the player come up with a theory and persue it, and it is one that I am giving much thought.
One of the challenges that I am presented with, though, is that the player is VERY new. Never played before. Thus, I'm not sure how to not reveal so much that he is overwhelmed (and let's admit that ArM has grown to the point where the spectrum of choices really can be overwhelming) but at the same time not hold his hand too tightly, either.