The fact is, he can't do the job obviously like the University hired him to do. However, I'm guessing the University's hands are tied a little due to the ADA. Not sure you could fire someone simply because they have Epilepsy.
As I said above, I just hope he finds a way to get healthy and continue. He is a great coach.
Sudden death IS a serious problem for epileptics, accounting for up to 20% (1 in 5) deaths in epileptics. No one knows why, but severe seizures can echo through a person's systems and result in cardiac problems and other events that can end life.
There are plenty of sources in that Wiki article, and on MedScape to look at for anyone so inclined. I sincerely hope that he makes the right choices for himself and his family first, and for football second. Of course, only he and his family can make those decisions, but it is heartbreaking for myself (and I assume the rest of you) to see this on such a public stage. The bright side, I suppose, is it probably leads to greater awareness among CFB fans, at least.