I would very much love to see the "simple CRDT" implementation described above, seems like it would be a great learning tool and/or foundation on which to build something more complicated!
The CRDT I was referencing was Shelf by Greg Little. He's given a few talks about it at the braid meetups. When he first showed it off, Kevin Jahns (the Yjs author) was also there and was as impressed as I was:
https://braid.org/meeting-8 (the shelf part with Greg starts at about 43 minutes in to the recording.)
The code is all here. Its tiny:
https://github.com/dglittle/shelf