Assuming the engines to be perfectly reliable (100% reliability no matter the conditions), what is left on the aircraft that is now more of a factor in terms of adversely affecting safety?
Put another way, of ALL diverts of aircraft flying hours away from the nearest suitable, how many were due to something NOT engine related?
Any figures?
EDIT to add:
The greater chance of an engine failure "early on" in a 4-engine bird is an "insurance payment" for greater safety when out somewhere in the middle, more or less.
Agreed that more engines increases the risk of an engine failure, but what is the chance of a 4 engine suffering dual-engine failure compared with a twin suffering dual-engine failure?