edmundronald:
It seems to me the ability to diagnose a failing engine is probably reduced by the closeness of a well-functioning engine to its failure regime. So if the engine were a bit overdesigned, it would probably give more warning of failure - and would also offer some more reserve engine power when other engines found themselves unwilling to supply such ...
All well and good, except that
overdesigned means
overweight, and profit margins make an overdesigned product uncompetitive. Gerhard Neumann, longtime head of a major engine maker, was notorious for telling his engineers "If it works right on the first test, it's too heavy!"
And "reserve engine power" means excess assymetric thrust, and that means reevaluating the whole aircraft to be sure the pilot can keep it flying straight.