Cees De Groot wrote:
 > we're close to an
> image format change (presumably for 4.x), which means you'll not be
> able to upgrade by means of an update stream anyway.

Why? pass a new version of the image tracer that does the conversion 
through the update stream, have the last update run it and ask the user 
to open the new image that was prepared for him and named so and so.

This is not completely automatic, but its much much easier than 
integrating the simplest problematic change manually...

Daniel