I might be way off here, but does PyPy-STM works at all with the new stdlib asyncio? I mean, the whole purpose of asyncio is running non-blocking I/O in a single thread and delegate blocking CPU-bound executions to other threads (with the run_in_executor method), but it would be awesome to share the asyncio loop event between multiple threads. I don't know if this is possible though.
asyncio would need some work in order to be trully parallelizable on top of pypy-stm. You would need to go around and eliminate all the global state that all the elements are modifying. But in principle it should work (requires work though)