What is possible when a route involving a mastūr narrator gains reliable independent corroboration?

Innovation, Defective Retention, Ikhtilāṭ and Ḥasan li-Ghayrihi

• Every report of the mastūr instantly becomes ṣaḥīḥ li-dhātihi
• The report as a whole may gain an acceptable grade
• The mastūr narrator becomes a Companion
• The two chains automatically become mutawātir