[pshc]

I think CRDTs make sense for your usecase.

Maintaining the shared state with REST calls that overwrite parts of server state is indeed brittle, and really only suitable for overwriting fields on flat data records. It also requires that you consider server-client state coordination with care at all times, and things can easily get out of sync in non-happy paths.

Like you said, building out a CRDT which specifies how updates are coalesced will significantly reduce cognitive burden.