"if it was done by Boeing employees on Boeing time, it's suddenly interesting."
Right, because, I think, if Boeing tasks a designer and pays him for his work, Boeing will
have some kind of interest in the result.
If you replace "Boeing" by "Junkers" or "Focke-Wulf" (or maybe even "Sukhoi" or "Mikoyan" ?),
I think, matters may be sometimes a little bit different. During times, when the aim was just
to keep the design team complete and intact (alive !), there may have been designs by a
real Junkers designer, using Junkers paper and with Junkers pencils for drawing a design ... his
company never had the slightest ambition to even consider it !
But generally "No manufacturer seems to have expressed an interest" should be a good point,
I think. Amateurs mostly aren't just the inventor or designer, but double as "manufacturer ",
so they are "in",exceptions from that rule perhaps could be design Bureaus/thinktanks like
Bauhaus Luftfahrt e.v. (http://www.bauhaus-luftfahrt.net/) or even Avpro ?
But probably not Monsieur Luigi Colani ! ;D