I've done this dozens of times, didn't seem like that big of a deal? I think the place this might have fallen over is the "updating symlinks" part. Don't replace the system Python, install yours alongside it. They don't need to know anything about each other; aliases in developers profiles and full paths in services/scripts.
Yup, stick it in /usr/local and place that in your PATH and Python search path before other dependencies. If you want to be fancy, put it somewhere in your home directory so other users on your same machine cannot be affected.
It's really not hard. I do this with other compilers and don't really have issues, though I tend to package it up into a container if I'm going to ship it (e.g. build environment for a team, interpretor for a production service, etc).
