TDracer, I see you’ve read the commercial about “power by the hour”. I suspect the reality is slightly different based on my own experience.
In particular the bit about strategically placed spares, RR have bean counters too and they probably don’t like the idea of spare engines sitting around at remote airports either. Furthermore there is the question of the modification status of each module - this doesn’t always go with that, the question of matching life limits on modules to avoid frequent engine changes, and of course if it’s a generic spare, it would have to be “dressed” to suit the aircraft customisation.
I love the idea, but I suspect the reality is different.