Yes, that would be a mess, but the master public key can simply announce its currently in use subkey by establishing this relationship in its kind 0. This effectively creates a signed 'certificate' that links a master key pair with its subkeys. Additionally, subkeys must also specify this relationship in their kind 0, providing two-way verification since both the master key and subkey certify their connection. In this way, the master key pair becomes the source of truth for where to find the current activity of the user/entity. There maybe more details and edge cases to cover, but for a note it's enough, happy to keep discussing 👌