Interesting. We have no plan to support such a feature. I just don’t want to give you false hope. But will see. If hosting out of the shelve npm registries turns out to be too hard/complex for people, we could consider this alternative approach.
Btw, were you aware that the Unity Package Manager supports Git URLs project dependencies? Git support on Package Manager
Thanks a lot for sharing. This gives me another perspective 
Regards,
Pascal