Have you seen Ink & Switch's Upwelling (https://www.inkandswitch.com/upwelling/)? I think you might find it at least a little interesting, although it's more focused on non-fiction (where you trust all parties) than contracts. From a user perspective, it provides version control, diffing and both collaborative and private editing, all things that seem like they would be very useful when creating & editing contracts.
I had not seen that, thanks for sharing. As you said, this is a different kind of version control from what we offer, but I think we could borrow some of their ideas, or at least use it as inspiration. It's very cool
