Okay, completely restarting python is not really necessary. Being able to reliably unload and later on re-import python modules (extension modules as well as pure python modules) in an embedded python runtime would solve my problems. 

One way to achieve that is currently Py_Initialize / Py_Finalize, but there are the drawbacks already mentioned. Another possibility is using sub-interpreters. 

If either of these could be fixed for extension modules (possibly with unloading the shared objects / DLL's :) ) I'd be fine.

I completely understand your point about backporting and it is not an issue.