True "Undo" is, IMO, a pipe dream for all but brand new projects. That will pretty much require you to rearchitect a decent chunk of anything that wasn't built with it explicitly in mind.

In this case, I don't quite understand why stars and forks need to be deleted when switching visibility, since it seems like the two shouldn't be linked. I can star and fork my private repos just fine, so it seems like it was just easier to clear it out than to deal with RBAC at that level.