Last couple of days I worked with Pablo on trying approachs for enhance performance of the backends.
Most important, we tried approachs to run the VM in a worker thread, freeing the main thread. This is important because if we want to have a responsible UI, it cannot freezes when executing a VM process. And the UI process needs to run in the UI thread (at least on macOS, I think windows and linux are more permissive).
Now, this caused several problems on FFI callouts/callbacks that we needed to address. And when you play with threads, you always have running conditions, etc.
So well... no much progress in that area. But at least now we understand better many of the problems associated to it.