Unfortunately, if you want your scripts to be portable to other POSIX systems you might have to use the short options, as the long ones are not standardized. You have to decide the tradeoff for yourself.
But yes, that is nice.
It's exactly the same thing people initially loved about docker or vagrant.
I don’t think any of the other options you specified can manage the same thing.
Neither pacman, apt, nor any other package manger require any sort of virtualization. pacman works fine where-ever you have a C compiler including macos, linux, windows, probably even TempleOS. Whatever you want.
If you want to add something to the user environment system wide, the traditional thing to do is to dump a file into `/etc/profile.d/` which will be sourced during shell startup. If you instead want something local to the project, you just make a script that the developer can source, like a python virtualenvironment.
I'm not saying any of these ideas are bad. I am saying that they are easily solvable and have been solved for the past 20 years. Without Nix.
All of them except for GNU, AFAICT? (That is, only GNU seems to have long options.) Checking manpages for rm(1) as a simple reference, I can't see long options in any of the 3 major BSDs or illumos, and checking Alpine Linux seems to show busybox also only doing short options (sorry, can't find an online doc for this, though it's easy to check in docker if you don't have a machine running Alpine handy). OpenWRT also uses busybox and has the same (lack of) options.
https://man.freebsd.org/cgi/man.cgi?query=rm&apropos=0&sekti...