Unlike Stewart, who gave a single lecture at an ethics conference, William Lerach could be more heavily involved in teaching the basic legal ethics course at Pittsburgh. Lerach's sentencing memo (see page 25) suggests that he wouldn't be the primary faculty member in charge of the course, but that he would simply be a regular lecturer in pre-existing courses. (The memo is somewhat unclear as to how much authority he would have in the classroom.)
I don't see a problem with using Lerach as a frequent guest speaker in an existing course, though I would have more concerns if he were going to be the primary teacher for the legal ethics class. It is pretty common in legal ethics courses to invite guest lecturers to talk about their ethical violations, so I don't see Lerach's involvement in an ethics class to be extraordinary if it takes that form.
But if he were asked to teach his own course, I think that would send the wrong message to students. Whereas a lecturer can be held out as a cautionary tale, the person in charge of the course is being held out by the law school as an expert on legal ethics. Lerach can certainly tell the cautionary tale, but I don't think he should be held out as a legal ethics expert for students. The sentencing memo suggests that Pittsburgh is erring on the right side of this line (just as I think Hofstra erred on the right side of this line), but the details of this proposed arrangement are still a bit unclear.