On the subject of incapacitation. Without full expert knowledge of whats happening, most of what happens to the other guy may also be about to happen to you.
I have had food poisoning from catering. This happened on the same day as my capitan also came down with food poisoning. We ate different food from different catering packs, but supplied by the same caterer. He told me he wasn't feeling too perky, I continued as PF. The flight was only 45minutes in total. about 20minutes in.
About an hour after on-chocks, he was almost totally incapacitated. About 2 hours after that, so was I. We ended up stuck in a hotel for two days too sick to move.
The subtle nature of this type of incapacitation is often spoken about in CRM courses. The reallity is quite sobering. If the flight had been longer, remote or whatever, the situation might have become serious.
We didn't declare a pan or a mayday. At the time it was not 'needed'. If things had developed more quickly for him, I hope I would have put out a Pan at least.