Absolutely. And as a next step, you distribute your OT per document so that no one of them has too much load. This is exactly how Google docs work and for the most part it works well.

The downside is that if a single document gets a spike of traffic because it goes viral, then that document won't scale.

Right, bur could one of the clients be elected to the OT leader role without having tje smarts at a backend? I guess it boils down to trusting the integrity of the client.