As a temporary patch, remove the ability to remove users from the default org. The UI today has 2 modes, "Mutli Org" and "Legacy" (for lack of better words). The legacy requires the users to be in the default org. The experiment therefore is not backwards compatible if a user is no longer in the default org. To simplify things, keep users in the default org.

This guarantees users always belong to a single organization, which simplifies edge cases and prevents orphaned users.

This will likely be removed in the future.