While I understand the desire to save typing, I would prefer to unroll this bit of meta-programming to actual 'class' statements.  For justification, see  my rants on unit testing:

- https://palladion.com/home/tseaver/obzervationz/2008/unit_testing_notes-20080724
- https://palladion.com/home/tseaver/obzervationz/2009/unit_testing_redux-20090802

One item not noted there:  using a real 'class' statement to do the mixins makes tracebacks sane.