So this seems like a confluence of both supporting compressed files for loading source code as well as supporting new archive formats (e.g. xz vs. tar); zip just happens to do both implicitly. And there is also the question of if you explicitly plan to do this in C code or in pure Python as I plan to introduce a pure Python version of zipimport into importlib for 3.4 so that it can use zipfile directly and thus all of its full support of zipfile abilities.

And there doesn't have to be any performance cost in trying to write bytecode files; it's very simple to have a loader which simply skips that step entirely.