But this is not necessary. The python developers just need to specify this fast subset of the language, and let people use to create libraries. Over time, we would have a growing set of libraries written in the fast subset.
I would guess that there's a clear separation of responsibilities, and each of the two languages is very well-suited to what it's being used for. There's not really a whole lot of anxiety about getting Lua (or whatever) to pull out all the stops you see in a compiler like SBCL or interpreter like V8, because these communities were never looking for a single language that could cover all uses cases in the first place. To steal an analogy I used the other day from myself, I'm guessing they don't want a spork all that badly because they're plenty happy with using a fork and a spoon.
That's how the community of people doing scientific computing and suchlike in Python tends to feel about things, too.
It currently emits Cython for the C-backend (and PyIodide). It is very alpha currently, but if people are interested in helping, get in touch.