After more thought, I think the existing behavior is probably what we want.  There may not be a clean way to allow access and updates to non-locals.  Even if a way was found, it may tie our hands and preclude other implementation changes down the road.  Also, such a feature may be at odds with the current API which allows the execution environment to be retargeted.  There is also a risk of introducing new security issues.

I've attached a PR to update the eval() docs to reflect the actual behavior.