I have the same goal. I also don't hesitate to use some abbreviative tools for repeated code, maybe. But only if it helps to simplify, not to change the language. I was only thinking about the actual build process, not about the language itself.
Furthermore, thinking of macros again, they make [...] I 100% agree with you. Changing the language isn't a good idea.
XML on the other hand, as an intermediate language or for pickling makes sense to me. At least it is easier to parse than Python. (But we *have* the parser...) I thought about using XML as a formal description for generating stuff. For example CastorXML (a java xml databinding framework, http://castor.exolab.org) uses XML Schemata to generate simple data classes with XML marshaling/unmarshaling functionality.. Though I'm not sure at which part of the MiniPy build process generating code could be useful, I think it should be kept in mind.
"Premature optimization is the root of all evil." -- Donald E. Knuth