Honestly, there is a lot more I'd like to do with my life than caring about some debian packaging practices when all I want to do is ship a company's internal application with it's exact dependency versions. But it needs to work, and, e.g. "The virtualenv relocate-able flag has been always experimental, and never really worked;"

So in practice we're back to shipping whole distributions using Docker (or, like we did, abandon Python as an option for development but keep .deb packages for deployment).