[bumelant]

I don't think this has strictly something to do with the state in REST. This is about state of things changing in general.

What you can do about it (other than creating something along the lines of your idea) is to create a history/snapshot on updates. I'm pretty sure most languages/frameworks has something for that, in Java/JPA you can do this by using Hibernate Envers' revisions. Exposing these revisions via REST API pretty much is what you suggested.