not really because as I said UnixProcess already has an implementation for doing this, you dont need any of those protocols/libraries you mentioned, it does not even need Fuel. It already works.
And the reason why I mentioned Python multiprocessing module is because multiprocessing does not only implement a specific way of communication between processes its also handle concurrency issues like data synchronization and much the of messy problems that come with concurrency.
And this is the are of improvement, its not what kind of format the communication is , as you said it should be up to yourself how to format your date, maybe you want json, maybe fuel, maybe you have your object and classes. The real focus here is true concurrency issues on may experience because you will be having two image running alongside with no guarantess when one finish on action and framework to synchronize data.
Obviously one can implement his own but I think Pharo would greatly benefit to have an establish default framework , even a small one for OS-Process concurency.