I'm trying to setup Python3 and Python2 via mod_wsgi on Ubuntu, so I've installed the mod_wsgi_py3 package but also wish to run the py2 version and have it switched depending on a flag within the virtualhosts config. Is there any way to do this withing Apache 2.2?
No, it is not possible. you would need to run two Apache instances, each with different mod_wsgi binary compiled for the Python version you want to use.