Adding Larry in case he remembers more color. (Larry: the key question here is whether some version of this (like the one I've been working on, or a simpler one that Eric has prepared) is viable, given that any time someone works on one of the frozen or deep-frozen stdlib modules, they will have to run make (with the default target) to rebuild the Python binary with the deep-frozen files.

(Honestly if I were working on any of those modules, I'd just comment out some lines from Eric's freeze_modules.py script and do one rebuild until I was totally satisfied with my work. Either way it's a suboptimal experience for people contributing to those modules. But we stand to gain a ~20% startup time improvement.)

PS. The top comment links to Eric's work.