If Boris dies or becomes unable to function as PM, we get Dominic Raab, at least in the interim, he's first secretary of state and we don't have a deputy PM right now. Raab is very right wing and comes across as a bit of a sociopath- if he decided on herd immunity to save the economy, I doubt public opinion would change his mind.
I also do think it would be unsettling to people if Boris were to become seriously ill. I do think there are more competent people around- but not in Boris' cabinet!
I think he does look unwell (when we have seen him) but not that seriously unwell. However, 7 days is the point where people can take a turn for the worse, so hopefully he hasn't become more seriously ill.
He's made some awful decisions so far, but I would like him to be around to be held to account for them.
FWIW, if we follow our current track, we will be one of the worst affected countries in Europe, though.