The concept of an "Uncommons" as defined as either a new set of rules, or as an alternate to WMF-hosted websites is not going to solve our current problem of lacking images to support our educational goals. We should be discussing how we can continue our mission to disseminate the sum of all knowledge when we are handicapped by copyright laws, period.
Fruitful discussions deteriorated when the issue of the "URAA-restored copyrights" [1] launched the Commons discussion in 2012 [2] which led to mass deletions. Since then we have seen some undeletions, but in general the whole drama of it has become too complicated to explain to the people we care most about, which is our dwindling body of contributors across projects. I tend to contribute well within our current Commons hosting parameters, but every now and then I step out of my comfort zone and feel as Fae has described in his mail above.
I really like Gerard's idea of somehow linking images on WikiData, which will help significantly with discovery by readers and also serve as self-explanatory templates for multi-language users. However, though I firmly agree that we should proceed along those lines, this still won't solve the core problem, because even on WikiData we cannot make interwiki links to *all* images we need and I personally believe we shouldn't try.
I think that the only real solution for our educational mission going forward is to let WikiData take a similar approach to what Europeana is doing for European museums. There are lots of specific organizations on the internet working on exactly the same copyright problems we are, but they have a huge advantage that we don't have, which is that they are focussed on a finite set of images. We often end up talking in circles because we want locally hosted images for "everything". If we take a collaborative approach, we can either include a link to a file, serve our readers a reduced preview of a file or serve a full-fledged image-viewer-enabled version of a file, all depending on whether the physical location of the file is in the Wikiverse or not. If we set this up, we might make it possible to "cross-load" individual files from Wikipedia and vetted external projects via WikiData to Commons rather than force people to upload with the default Commons uploader.
What I think we need is a good illustration of the scale of the problem, which admittedly is hard to show. Personally I was very upset when images of artworks by Leo Gestel were deleted last year [3], even though I was not the uploader who put all the work into all of those artwork templates on those files. My niche interest on Wikipedia is 17th-century painters, but I have also worked on colleagues of Leo Gestel whose works cannot be shown at all in their Wikipedia articles, just because they "forgot" to date their paintings. I have noticed a "copyright gap" occurring when Wikipedians give up trying to illustrate such articles.
When that happens, we all lose. Not only are we missing the Commons images, we are missing work on the corresponding Wikipedia articles. I made a comparison of Wikipedia artists matched against a dataset of painters which illustrates a small piece of this "copyright gap".[4] Another interesting gap occurs when you look at the work of painters vs. artists who ventured beyond two dimensions, such as sculptors, furniture makers, porcelain artists, and instrument makers. We cover painters and printmakers so much better, thanks to Bridgeman vs. Corel, as long as we ignore the fine print.[5] The OTRS system for image release by an artist's direct heirs is the only alternate route, and there is no alternate available for orphan works that I know of.[6]
In general, Wikipedia has much better coverage of "really dead" people as opposed to "not so dead" people. Discussion regarding the problems of BLP's is often made without realizing that they are actually edge cases compared to the large group of people born after 1800 and who died before Wikipedia began. This is a combination of the copyright gap and the frustrations of experienced contributors who have had their hands slapped on Commons and other projects.