For anyone else who comes across this thread, this user replied to me privately so I responded there.
The summary of what we discussed:
I contacted the developer of that fork to ask if they would be willing to let me add their extensions to the version of Scratch running in ML for Kids - they very kindly granted permission for this -
https://github.com/MrYsLab/s3onegpio/issues/85 This is not going to be a quick piece of work, so it may take me a little while - both before I will have time to start, and to actually do the work itself.