I wonder if Python's metaclasses would get you what you're describing. Some thought would have to go into the primitives required to generate the constructs for the destination language(s), but metaclasses would allow you to serialize to different languages fairly easily once the primitives are in place. This approach isn't nearly as elegant as Lisp, but I think it takes what you're describing out of the "pretty much impossible" realm.

Overall though I agree with you, I just had a slight disagreement with the "pretty much impossible" claim.