If our objective is to produce what really made HyperCard a tool for
non-programmers to use, rather than creating yet another app builder in
Python, then we can't have a code-generator. It has to create a file or
set of files that represent the objects and their behavior such that a
person I call an Inventive User can build useful things with its
widgets and scripting.

I'm not sure that is or ought to be our objective, but it's what I get
out of the name "PythonCard" and Kevin's involvement with the project.

That said, I'm also in favor of XML as the intermediate description
language just because I think it opens the resulting stored objects to
a huge amount of other uses, including, of course, Web-based apps and
UIs.