The point raised about the same component existing on the second engine and so forth ... on an ETOPS thread a few months ago, someone kindly spelt out the details of ETOPS.
Things like - each engine must be worked on by a different team, so that the same human factor mistake cannot take place.
I have to say, after reading the long list, I was greatly reassured but ETOPS is driven only by money. If it is cheaper - they will do it.