When I say "thousands coming and going" I'm talking about trying to run rqlite on, say, a network of cellphones. When people ask me about this, it usually means they have the wrong mental model of what rqlite is.
However, running it on Kubernetes should work quite well. Check out the documentation at https://rqlite.io/docs/guides/kubernetes/
>If a node dies due to, say, hardware failure, when it rejoins is it seen as a slightly out-of-date existing node since it’s part of statefulset? If so, assuming quorum is maintained, this is probably a lot easier than I was making it out to be.
Assuming I follow you, yes, this should work fine -- and exactly as you expect. I suggest you try it out, and if you don't understand what you're seeing file a ticket on GitHub, or join the rqlite Slack[1].