Musea is hoping to get the new, 4.x site up in a few weeks, and with that will come the download package (already ported) and the ability for us to set up a repository. We could set up separate 3.x RPM and 4.x RPM repositories with the various downloads you mention available under them.
You're right, the SDM doesn't cover the kind of release scenario you're painting well. But we could set up SDM packages for the 3.x and 4.x RPMs in order to give folks a central place to report bugs, and include a pointer as to where to go to dig out the exact set of RPMs they need to download.
I've already been thinking about the need to integrate the SDM with the download package. aD may've already done this a bit with their work on the SDM.
