Don't think you need to worry and I personally wouldn't open a Pandora's box by asking too many 'what if' questions.
So long as both crew are legal when the flight departs, what happens down the line falls into acts of God, Allah or unintended consequences. Even if the other chap has died on you, you're still flying 'as or with a qualified co-pilot'. You're not going to sit there with a dead Captain and refuse to get the aircraft back on the ground because of a possible and very tenuous technicality are you?
In the never so humble opinion, I'd not worry about it at all and just proceed on track or as directed by common sense.
Toodle Pip!
Best of luck.
