I'm pretty sure you could design a SaaS offering in two parts: one that sells you a digital copy of a thing as a product (rather than a license), for delivery to a digital storage locker; and then, the other, a digital storage locker.
Oddly enough, Apple already has a digital storage locker, called iCloud Music Library. It's where your uploaded songs go when you use iTunes Match and the song doesn't actually match any entry in the Apple Music library.
If iCloud Music Library were properly designed (it's not), your purchased, matched, and uploaded songs would all be available permanently through iCloud Music Library in its capacity as a digital storage locker, whether or not they're still available through Apple Music. The licence-holders wouldn't be able to do anything about this: this isn't Apple broadcasting a song, this is Apple acting as the moral equivalent of bank, offering a safe-deposit box service, where you hold a box into which you've put a USB stick containing the song you bought from them.
Sadly, the synergy between Apple Music and iCloud Music Library is actually exactly the opposite of what anyone would want: when an artist's license agreement with Apple Music expires and their tracks are purged from the system, Apple will actually delete not just your purchased licenses from your iCloud Music Library; and not just the licenses of Apple Music tracks that fingerprint-matched local copies you had; but even your uploaded (!) copies of songs by a given artist that didn't match any Apple Music license, but just happened to have ID3 information corresponding to the artist whose rights were expiring. (In that case, the tracks still appear as entries in the iCloud Music Library list, but they're under a permanent "waiting" status, because their backing storage has been removed. There are many support threads about this issue, none with answers—well, that's what's going on.)