Good points I didn't think of.
Agree with your statement, after all the 3rd did avoid Naruto's RS, and it took clever coordination and speed from Naruto's chakra arms to hit him. If he is hit with Enton, I don't see what's to stop him from serving one of his limbs, and to let it regrow, that's If he doesn't do full body like Itachi did Nagato, even then Enton could still have no effect on him or his mobility and he will still attack Sasuke while on fire. This is assuming Sasuke can even land enton on him, because the 3rds speed was better than the 4ths, and Sasuke had a hard time keeping up with the 4th.
You're also right, with out intel, Sasuke would be in a bind.