Supporting multiple interpreters in a single process is not what most people mean when they talk about removing the GIL. Objects from one interpreter could not be used safely from another interpreter. This would be handy in a few situations but is essentially not all that different to multiprocessing.

What people usually mean when they talk about removing the GIL is having multi-threaded code make use of multiple cpu cores (as it does in Jython.) This would involved splitting the GIL into more fine-grained locks. Unfortunately experiments taking this approach have so far shown significant performance impacts for single threaded code.