I haven't had much luck with pip and at least Python 3 running on OpenWRT. It will install pure Python packages to the "root-level" Python instance, but does seem to fail for venv use.
I've poked at that exact package myself and was planning to build it within the OpenWRT build system, but a couple other things have gotten higher priority than figuring out what's wrong with my attempt at a package Makefile. Wrapping it as a package would be the approach I'd suggest.