I think lack of demand, and a fragmenting of the component standards, are hurdles. Those old Schwinn (and other brand) frames were made during a time period when there was a lot of interchangeability, and most spare parts are still available. Today, standards for things like bottom brackets change every three years. There's no part on my 1985 frame, that I can't replace today, cheaply.
I can get a brand new lugged steel frame that would be perfect for my use -- a Surly Cross-Check. Seriously the only deterrent is a minor injury has forced me to re-think what my future needs are for geometry. I may need to adopt a more "comfort" posture. Better than not riding. Sucks to get old.
Despite my above comment, and thinking about it more, I want my next bike to be modern in the sense of accommodating fenders and much wider tires. I need horizontal dropouts and to be able to set the rear dropout spacing, to accommodate an internal gear hub (IGH).
>Today, standards for things like bottom brackets change every three years.
Your comment is almost a decade out-of-date. Everyone these days has mostly converged on the same threaded BB standard for all but the highest-end bikes. Those press-fit BBs caused too many problems.
> Seriously the only deterrent is a minor injury has forced me to re-think what my future needs are for geometry
A Cross Check with a flat or alt bar and 30 mm of spacers underneath? That or the Soma Doublecross without all the spacers. The main triangle and the fork are build from heat treated Tange Prestige tubes like some of the ATB frames of the '80s and '90s, unlike the Surlys which are built from utilitarian 4130 chromoly. Or the new Disc Trucker with extended head tube and the new Truck Stop riser drop bars. They shortened the chainstays and it no longer rides like barge unloaded, like the previous model.
I went through the same hurdles after an accident some ten years ago, built several bikes in the meantime including a classic road bike with somewhat similar geometry to the Cross Check, which I knew was not for me. Turns out that it's manageable, although I would probably not use it for a 100k trip. My current go everywhere bike is similar in geometry to the Double Cross, but it's aluminium.
I would encourage you to get in touch with a reputable custom frame builder and describe your situation and requirements. The local shop I use has been in business for nearly 50 years, and they use components that I can best describe as "tried and true." A bike they built for me in 2014 is something that I can still fully service myself with commonly-available parts and tools.
Meanwhile I damaged a thru-axle of a high-end big-name brand bike (rhymes with "wreck") I bought 2 years ago, and they told me that they no longer stock that part because it's "obsolete" (!)
I can get a brand new lugged steel frame that would be perfect for my use -- a Surly Cross-Check. Seriously the only deterrent is a minor injury has forced me to re-think what my future needs are for geometry. I may need to adopt a more "comfort" posture. Better than not riding. Sucks to get old.
Despite my above comment, and thinking about it more, I want my next bike to be modern in the sense of accommodating fenders and much wider tires. I need horizontal dropouts and to be able to set the rear dropout spacing, to accommodate an internal gear hub (IGH).