When it comes to venv-related stuff I feel like Chris Siebenmann has been gradually independently discovering things that are fairly well known in the right circles.

A properly relocatable venv would require redesigning up front, along with cooperation from installers (i.e. they need to not put un-relocatable stuff into the venv; specifically, by not hard-coding the venv's Python symlink's path into generated wrapper scripts). (Or a relocation tool could perhaps fix the wrappers.)

I actually do have some designs for this. It definitely should be possible.