@icon_of_computational_sin Yes, I am interested in the idea of being able to install multiple versions of a package. I think that most of what's needed for it is already in place in arch (I won't speak of other distros, but I think the things I am looking at are, at least, linux-standard).

>They don't allow installing software without root permissions. They don't allow local sandboxes, because all software must be installed according to man hier.
Well, these two go hand-in-hand, and pacman DOES support the latter (though I don't know how to use it), but apparently not the former:
yun-wuxin:[wisknort]:~/temp$ pacman -Sr . inxi
error: you cannot perform this operation unless you are root.
yun-wuxin:[wisknort]:~/temp$ sudo pacman -Sr . inxi
[sudo] password for wisknort:
error: failed to initialize alpm library:
(root: ., dbpath: ./var/lib/pacman/)
could not find or read directory

I'll grant that it probably should.
I am somewhat interested in nix, but after lurking their matrix room for a while, I am less interested. It sounds like a good premise but it seems in practice that it's just another way to overcomplicate things... I ought to try it out for myself sometime.