bd_
Specifically, I would like a clear point when I can know, for sure, that:
  1. We know whether we are the instance master or not
  2. RequestOwnership is expected to work normally
  3. We can call GetOwner on any synced object (or at least the object receiving the event), and get someone who, if not the current owner, is at least a prior owner of that object.
  4. We have observed player joins for what was, at one point after we started the join process, a complete list of players in the instance.
Currently this is a bit difficult; we can guess that, maybe after OnPlayerJoined or OnDeserialization things might be settled enough, but that might be later than necessary. If we're the first player we can only rely on OnPlayerJoined, but the first OnPlayerJoined is too early to have observed player joins for everyone who might be the owner of an object.
In particular, having a clear signal of whether we are the first master (and can freely set the initial state of objects) or whether we are expecting to deserialize object state would be very helpful.