Maybe they could have two versions of the interpreter, one that’s thread-safe and one that’s optimised for single-threading?
Microsoft used to do this for their C runtime library.
That's exactly what we have now and it looks like the python devs want a single unified build at some point
PHP does this as well. Most distributions ship PHP without thread safety, but it's seeing more use now that FrankenPHP uses it. Speaking of which, it would be nice if PHP's JIT got a little love: it's never eked out more than marginal gains in heavily-numeric code.