Next - Bigmoose went to different places on the EXPRO site. He highlights an excellent feature (internal inspection of BOPs) which, whilst it makes my untimely comment look dumb in one sense, adds to the point I made. The capability to do wonderful things is there. It just needs to be applied in a whole through-project manner with some proper FMEA. Analysis of the BOP is useless if it takes 5 hours to undo a single nut and you need to undo 12 nuts before you can start to intervene.
I agree with your ‘systems’ premise when it comes to maintainability, however relying on ROV intervention is questionable as weather etc can cause problems. Personally, I would prefer we didn’t have to manipulate bolts with an ROV, sounds way too much like working on a steam engine 200 years ago.
It is possible to make a BOP system both far more modular and far more redundant, and recoverable and maintainable in increments.
The annulars detaching with the LMPR is one step along the way, it is certainly feasible to move much farther down this path.