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'course the facilities in a ship's head don't include processing, reclaimation/recycling, waste treatment/storage, or water storage. all that is handled elsewhere, or not at all. but a starship's head must include all that, so it's not a good comparison.
You seem to think that each stateroom will have it's own system to handle it's wastes, why? People have complained that my fold down fixtures cause too many problems, but each fresher having it's own complete handling system won't. A spaceship would have a central processing system, aka as life support.
As for maintainence issues, i.e. being so much of it, what do you expect that the crews are doing during jump, playing cards 24/7. They are checking fittings which might have come loose, cabling runs, handling complaints of broken fixtures, etc., anything to keep them busy. Do you know for years that the US Military for years fought the introduction of reasonable footware for it's members because keeping their boots polished was something that could be done to use up time. Even after they went to reasonable footwear for hiking and marching, even in the field, recruits were still issued boots for parade.
As far as the headroom goes controversy goes, say you take the extra half meter of space from the 2.75 meter headroom and use it for storage lockers, say a place to store spacesuits, private gun racks, etc.. If the occupant is too tall for the 2.25 regular space, these racks can be modified or folded out of the way.
The real problem of course is that none of us are certain of a design and try to use what are esentially mechanisms approximately 5 TL's below what is being postulated. However I do like it, it is interesting to hear ideas from so many others