On the topic of keeping track of changes to conservation statuses:
I also very much want a better system for tracking these changes and I’ve done some thinking on it, but I don’t expect it’s a feature we’ll be able to tackle soon. There are a couple of related feature requests (here and here).
As @jdmore says, flags are the best tool we currently have for recording some context for these decisions, though definitely imperfect since flags are not a complete history.
A couple of times a year we do export all of the conservation statuses in iNaturalist. The one I’m looking at has 157,118. It is not very easy to work with on its own because it contains taxon ids rather than taxon names, but I am happy to share it by request if it would be useful because it doesn’t contain any sensitive information.