As far as returning Yoshimo to life goes, I seem to recall that the body must be pretty much intact if the person is to survive the process. Now what was it we did with that heart again?.....
Personally, I think it would be a better idea to make a new tidbit in Ascension: If Evil gods can bring people back from the dead, so can Good ones. Amelysan conjures up Jon Irenicus--and Ilmater blocks with Yoshimo.
(Ilmater is LG, so the point of whether or not this violates Ao's mandate that the other gods must keep their fingers out of the Bhaalspawn pie deserves scrutiny. It might be said that since Yoshimo's fate was bound to Jon's and the PC's anyway, Ilmater did not actually break any rules--or at least no more than Kelemvor broke by allowing the return of Jon, Bodhi, and the Five.)
This Yoshimo does not join the party, and is not the Yoshimo we knew and loved: He's no longer a real Thief, he's closer to a Priest of Ilmater. He is Blind, and helps to personify the essence of suffering by being a highly resistant damage soaker, but takes no real offensive action apart from his famous Traps. All in all, this could make Yoshimo a real stumbling block for Irenicus, which would be quite in character and a nice turnabout.
This could only happen if the PC removed the Geas, of course.
And it makes Ilmater look like less of a wuss, a much-needed change. "The Crying God" isn't exactly a moniker that earns one a whole lot of street cred, after all.