I can't really talk about Ruby. But PHP is much more static and surface of things you have to care about at runtime is like magnitude smaller and there already was opache as a starting point.
And speaking of something like JIT in V8 is of the most sophisticated and complicated ever built. There hasn't been near enough man hours and funding to cpython to make it fair comparison
Even for reducing the context size it's probably worth it. If you have to go back back and forth on both problem and implementation even with these new "large" contexts if find quality degrading pretty fast.