Interesting, how are you dealing with pacnew/pacsave files? From your explanation it seems that they would go into the read only filesystem and would need to be resolved manually and preserved there until some old version cleanup is ran. And while I find the idea of a writable overlay filesystem for the /etc fascinating, I think that could have issues with some rollbacks and backwards incompatible config changes. At the end of the day seems like a fascinating project, but I wonder if Arch+snapper wouldn’t be better overall.