I find your first statement questionable for 2 reasons. It is well known the RB211 is shorter than the competing big fans because of its 3 spool design allowing more efficient pressure increase across the compressor section and better matching of the combustion chamber. As for the remarks about maintenance costs, strange then that so many operators selected the RB211 in preference to GE and P&W for rather a large number of 747s and 757 and 767s?
I also very much doubt anybody seriously considered re-engining the Tristar with all the work and expense involved redesigning the wing and the S-duct and all the ancillaries- electrics, hydraulics, air compressors and all the other connections....now seriously- all that to save a small percentage (allegedly) maintenance cost? I suspect this is hearsay passed around the GE or P&W factory, at least one of which is located in Ohio? The problem with accepting the RB211 as the success it has been is the old NIH syndrome!