I've made some breakthroughs today, thanks in part to a couple sources - the dot com mailing list on yahoogroups and a local plastics company here in Denver.
The backstory - after struggling a lot to find the right pots that would extend beyond the plexiglass panels, i had placed requests for quote with several local and online companies for the parts below, or open requests to find ANYTHING that would match the specs i had. Very little luck - two quotes came back astronomical, and i won't be capable of paying $75 per pot for 100 pots any time soon.
I opened the question up to the dot com group, thinking there were probably DIY lurkers there. the back story to that is that I've been on that list for half a year or so, after lusting after the dot com synths for a loooong time. figured at some point there would be a convergence of a good deal and extra money.
Anyway, glad i went there - first someone sent me to a relatively obscure website that had pots made in very strange measurements, but the prime thing was that their bushings were just barely long enough. this is the site: https://taweber.powweb.com/store/ - not very familiar with weber audio components, but they do have a 10k linear pot which is most of the battle - and its under $2/pot.
But then after chatting with my wife, i went and looked for a local plastic fabricator, after still getting no answer whatsoever from ridout plastics. spoke to a guy named Randy - and not only did he give me a pretty decent estimate of time and cost on the spot, he is also a musician and had some inkling of what i wanted to accomplish, which is nice. my wife and I had discussed the idea of a countersink already several times, but did not think it was very doable with the difficulty of drilling in plastic. HOWEVER, for about 20-40 cents a hole, the fabricator will do the entire hole and angled countersink for us with professional tools, laser cutters and cooled lubricants, etc! that's a pretty fair tradeoff for the shoddy job we'd probably be able to do at home, even with my wife's extensive tool collection.
Planning to burn the latest version of the visio/DXF design onto a CD or flash drive and take it to him early next week.
This is their website, and Randy was really helpful: http://www.plasticareinc.com/
This is a huge leap forward because not only is it a much easier solution to the panels in general, and ultimately not that much more expensive, it ALSO negates the need for any special pots - now they are all pretty much the same as anything sold in the basic catalogs.
Ultimarc shipped the buttons out yesterday, so they are enroute - and the illuminated square buttons can be powered by USB if the bulbs are swapped out for LEDs - confirmed this with a Suzo-Happ rep this morning.
Finally, Ken with Hale Micro (another shameless plug for this guy and his product) is finishing the build and custom firmware for my UMC's and will ship next week. that's really awesome that he is willing to go that extra mile.
EVIL EMPEROR VOICE: Everything is proceeding exactly as i have foreseen it.