Thanks for submitting this.  Nice summary of the different cases.  I think very few people have given this that much thought. :)

You need a patch for the docs if you want this to even get considered.  Then the main obstacle is convincing the team that the nice new logical behavior is worth the breakage.  I would be surprised if it got through.

And Python 3000 is not going to be the "subtle breakage" release.  I would give you better odds if your patch created new APIs instead, and *documented* exactly what's useful about the model you're suggesting.