I understand your argument. Yet, I am not sure classes with the same
name are reasonable here. Tix is too intertwined with Tkinter:

E.g a Tix user user can just access Tkinter widgets via Tix:

>>> import Tix
>>> print Tix.Canvas   # This is TkInter's widget
Tkinter.Canvas

>> import Tix.ComboBox #whoops, we've got Tix's combobox
Tix.ComboBox

As a matter of fact, Tix docs seem to explicitly recommend accessing
Tkinter stuff through Tix:

"""The former imports the latter, so to use Tix with Tkinter, all you
need to do is to import one module. In general, you can just import Tix,
and replace the toplevel call to Tkinter.Tk with Tix.Tk"""