_collections sounds cool, but the flip side is any python without the C implemntation would still have the slower startup, right?

No, I don't have measurements -- just that I have heard importing collections can have an effect on startup time.

Of course, it's only a cost you pay once, so maybe it's not a big deal.

On the other hand, I could make __members__ a caching property that doesn't import OrderedDict until it is used, and not use it internally -- and I can't think of any reason why the stdlib would need to access __members__ itself.