I just had a thought: we may be able to eliminate this behaviour without
mucking about in the package globals.

What if the import semantics were adjusted so that, as a last gasp
effort before bailing out with an ImportError, the import process
checked sys.modules again with the full module name?

Not a fully fleshed out idea at this point (and possibly symptomatic of
not being fully awake yet), but I'll bring it up in the current
python-dev thread anyway.