Not that it is ready for primetime yet, but guix solves this problem well by allowing each user/application to have its own dependencies of different versions while allowing them to still share if they want the same version.

May sound weird, but take a look:

https://www.gnu.org/software/guix/

The main distribution will only ever have free/open source software in it but it is trivial to make your own packages/package repositories and share them since it is just a guile code file.