-Amaterasu takes out COFRS after it's prepped or it takes out Naruto while he's prepping it.
-That's far weaker than FRS, and FRS would at best destroy V3 and leave Sasuke unharmed. V4 Susanoo would block FRS with little to moderate damage, closer to little, thus it'd block that Rasengan barrage with no damage. It's worse in Sasuke's case since not all of the Rasengan can hit him at the same time, meaning the damage Kurama took won't be the same as what Sasuke will take.
-Kawazu Naki paralyzes Sasuke, but Susanoo can still move and Naruto can't do anything to Susanoo in the short time frame where Sasuke can't move. FRS can't get past V4. COFRS takes too long to prep and Sasuke would still be able to use Amaterasu as his physical movements would be impaired, not his mental actions.
-Naruto would die LONG before this jutsu ever got prepped.
