Richard,
Thanks for the input. It is important that I get the details right before building, so I appreciate you ripping it all apart at this stage so I can assemble it again in my head and on paper. These processes can only lead to an improved construction.
In my experience with extended tunings, the short changer-movement tend to cause one problem in particular: lack of free-play between nylon nut and changer in neutral for lowest string.
On my "extended E" I have 3 G# strings and 3 E strings. Synchronizing raises and lowers on these "triples" was a PITA - actually impossible, with butchered and free-wheeling gear-down bellcranks. To get free-play on lowest G# and E strings I had to pull the bellcranks over so there's much too much free-play on the higher strings and pretty uneven travel-start. It works, and have for 20 years, but I would not mind having less travel on top of scissors for same pull-rod travel, for the lowest strings.
The upper raise holes do require high force and short rod-travel, but since this is mirrored on the relevant bellcranks the problem should be minimal. May require more pull-force than on most PSGs, but unless the pull-rods give/stretch or nylon-nuts pop off I don't think there will be problems.
I do have an option for fine-tuning bellcranks for sync'ed travel, in that I can position bellcrank axles out of line - place the bushing higher or lower than the others and even high at one end and lower at the other, along the profiles holding them. I can even make this "offset" adjustable if I want to, but since these axles are indirectly coupled to pedals/levers - doesn't matter much where a bellcrank axle is position with regards to where its pedal/lever is hooked up - I plan to have a few offset bushing-holes in the profiles to handle "impossible cases" if they pop up.
I do want straight pull-rods and adjustment via nylon-nuts at the end. Much less risk of skewing and/or stretching with straight pull-rods than with bended ones.
I am not the least concerned with what a tuner or frequency counter shows in real life - my frequency counter is for lab-control. I regularly tune my PSGs up to a quarter-tone off by ear - my "ear" isn't better with respect to accurate frequency without a tuning-fork, and play happily along as much off-fret as I have to to play in perfect tune with whatever tune I hear.
I tune out string-beats, which means I am only concerned with how well strings and changes are tuned together. Pushing strings with the bar to minimize beating is the norm, but I have grown a bit tired of wringing strings or avoid certain chords for certain pedal/lever-combinations. Thus, my 2-pitch changes will be incorporated in my project-PSG - to eliminate unnecessary irritation if nothing else.
As for the "spaghetti" mechanics... I have taken that into account from the beginning, and made provision for as much clutter as I can force-fit into the frame
All PSGs I have seen - including the WBS - have large frames/bodies that get in the way. Most only have access to mechanics from the underside, and all parts/details in them are designed and mounted for such limited access even if that means they can not be mechanically optimized.
My trussed frame with three lines of bellcrank axles can...
1: be accessed from all sides when covers are taken off.
2: access is even better with neck removed, which it will be during initial set-up.
3: two sets of five changers open up a space down the middle for playing around with pulls. Note here that the backbone can be removed separately, so a space of about an inch in width is totally open with a fully playable PSG during set-up and service.
4: slender profiles / trusses, of which most can be dismantled without frame falling apart, improves access.
5: in my pretty open frame all parts can be mechanically optimized, which amongst other things mean I don't have to "play it safe" with regards to shapes and dimensions.
May not be very visible in my sketch, but for instance the screws holding the pull-rod bellcranks securely on their round axles, are inserted opposite the rod-attach holes. Can be done on all PSGs, but those screw-heads sure aren't easy to reach inside a regular body without dismantling all rods. On mine I access them from above, with or without the neck in place.
Another detail is the "two sets of five (or six)" changer scissors. Apart from opening up space down the middle, the narrower changer-sets makes it easier to prevent "give" without oversizing construction.
The pull-rod bellcrank axles will be arranged and spaced optimally for pulls, with no regards to which pedals/levers/gears that operate each. This leads to shorter pull-rods and more exact and reliable pulls in line with the changer scissors.
The entire pedal and lever/gear frames along front and back can be taken off with no adverse effect on action and tuning - the PSG frame just isn't as strong without them. Since I will have stoppers on the pull-rod bellcranks, all pulls can be tested and tuned precisely without having actual pedals/levers attached.
Have probably forgotten something important in here, so just blow my design apart again. I am always ready for another assembly/tweaking process.