I am replying to myself here.
Because I’ve just tested @talves Github repo and changed the media folder into a symbolic link under /content/ while the original folder is under /static/
It works all right. But the interesting part is that Hugo thinks of the symbolic link as a section.
So /media/ does have its own URL and its contents are rendered even when under /static/ or even /data/.
Now that’s interesting.
There is a known hack to disable a section’s output and naturally I’ve tried it with this /media/ folder workaround.
I’m happy to report that with the above hack /media/no longer renders as a section and at the same time its contents are available for .Resources
Of course as @bep said everything will be improved if issue #3612 is resolved.
But this looks like a very promising technique since it opens up Image Processing beyond Page Bundles.