Craig - 

> When you get access to an image that has stuff you want in it, you
> should be able to tell your image to talk to it and negotiate what
> ought to be transferred

Your work along these lines is extremely cool, and your suggestion
brings upgradability back -- but at the cost of defeating the purpose
of the original suggestion: when you bring non-code objects back into
a newer image, the format of these objects may need to change, and
that may require a careful series of steps operated on these objects.
But that's exactly the kind of problem that Avi's suggestion was
designed to avoid, and hence it defeats (part of) the purpose of his
proposal. Ie. once you add a solution to patch this, that solution
might as well be used for code also.

Michal