Your idea is good but i think it has to be taken one step further. You should be able to import ANY module, third party or not, and specify under which version to run it. What we need is interop between python 2 and 3.

Just look at this thread. Everybody who disses python 3 does it for library support, library support and library support. If you could write your own code in python 3 but still use libraries remaining on 2.7 most people would switch in a heartbeat. After that it's just a matter of time before the libraries transition to 3. Now we are stuck in a chicken and egg situation where nobody wants to make a move.