purely from a passengers point of view, if I knew that just after take off, with 7 odd hours of flight ahead, one of the pilots was unwell/injured/incapacitated, I would be more than happy for us to return to the safety of the departure airport, for everyone's safety.
If nothing unforeseen goes wrong then I am sure the remaining pilot could get us there, but that's the trouble with the unforeseen.
Is it any different in safety terms to a twin engine aircraft loosing an engine on take off? You wouldn't carry on over the Atlantic, even though it could probably get there.
(I know this one has 4)