Performance idea: squeezing down file size

For the bike network tool, ultimately I'd like to work on and present some vision at a large scale -- like all of North or South Seattle (50-60MB right now, or 20 gzipped) or the whole area (270MB, or 100 compressed). The `Map` files are gigantic, but I have some ideas for paring this down and creating something smaller, containing less detail than what's needed for traffic simulation...