Alpine (apk) and Void (xbps) have similarly nice packaging systems.

I was having problems building wine. So I used the arch pkgbuild and just didn't do the install phase. Made compiling pretty simple. And all the outputs are nicely defined in the aur repo locally.

Does Arch support installing multiple versions of libraries?

Yes, but only if they're packaged separately. PKGBUILD is easy, so it takes very little effort to repackage older library versions under a new name (and patch dependents to use the new name) if you need them.

Not really. There are a few applications that can be installed because the install path different for each version, things like Java support this. But libraries like glibc, etc. are tied to one version so anytime those libraries change it triggers a rebuild of many packages.