> I understand many things can happen while importing a library. But for a specific program, its imports are usually fixed and very much likely the same between runs. That's why I believe a zygote/fork/snapshot feature would still be helpful to help avoid the startup delay.

I agree it can be useful.  It's different from your first post.  (Snapshot whole application, rather than just Python VM).
And this idea is discussed on Python-dev ML several times.

But I think it can be implemented as 3rd party tool at first.  It is better because (1) we can battle test the idea before adding it to stdlib, and (2) we can use the tool even for Python 3.7.