Did you consider using CRDTs for your document sync? It sounds like what you were implementing was somewhere between OTs and CRDTs and trying to create a standard event protocol for them?

CRDTs remove the need keeping track of all (or any just recent) revisions on the server as you would with OTs, your server can be stateless and just act as a message broker between clients.

Edit:

Should have followed your links, yes that’s exactly what you are doing.

https://braid.org/