I experimented with this at the EuroPython sprints in Berlin years ago.  I was sitting next to MvL, who had an interesting observation about it.  He suggested(*) all the constants unmarshalled as part of loading a module should be "immortal", and if we could rejigger how we allocated them to store them in their own memory pages, that would dovetail nicely with COW semantics, cutting down on the memory use of preforked server processes.

/arry

(*) Assuming I remember what he said accurately, of course.  If any of this is dumb assume it's my fault.