Sounds good, M le Directeur . . . except that I can't fault my Frankinelli and I have no space for yet another bike.
Well, Frankinelli's paintwork is crap and I don't enjoy carrying it through stations -- but then a 531 frame is, ahem, unlikely to weigh much less than a Cromor frame of a similar size.
Now, if you were to build it up and rent it out, I might be interested some weekend . . . but it would have to have gears suitable for the elderly, which would be a turn-off for other potential renters -- I can't think of any way this would be a good business model for you.
All in all I think I should work to improve my legs rather than my bike(s).
But once you think about mudguards, also think about removing them, packing them in your bike bag, and remounting them. Unless that's been planned from the start, it's likely to be a pain. Actually if I did want a new bike (not just frame) I'd re-digest this PDF about partially disassembling and reassembling complex bikes compactly and quickly.
Indeed, why settle for mass produced derailers when C S Hirose can hand-make you derailers too?