I'm a software developer and a user of package managers. A package manager that allows me to only have one version of a software package installed will inevitably get in my way if I need two programs that need different, incompatible versions of that dependency. It happens quite a lot in my experience.
Basically, you want to put two versions of the same file(s) into one file.
If you need two versions of almost same set of files, then
chose different name for the package, e.g. package-2, chose different base directory for package files, e.g. /usr/share/package-2, and chose different names for binaries, e.g. /usr/bin/binary-2. It's not a magic. Just look at examples, e.g. python2 and python3.
You can create your own repository, where you will be maintainer of your packages.
You can use it locally, as directory on disk, or you can put it on a server and share with others, or you can compile it using openSUSE Build Service, which supports OpenSuSE, SLE, Fedora, RedHat, CentOS, Debian, Arch, etc.: https://en.opensuse.org/openSUSE:Build_Service_supported_bui...
