Perhaps equal to Madara ems.
Nah, highly doubtful. Itachi's V4 was only as large as Sasuke's V4, and after he gained EMS, Sasuke's Susano'o stayed the same size, while his PS is only equal in size and power as BM Naruto's Kurama Avatar, which stands to reason Itachi's Susano'o would also progress similarly.
Meanwhile, EMS Madara was sporting a gigantic V4, and after stabilizing it's chakra made his gigantic PS. I doubt Totsuka and Yata are enough to fill the gap between Itachi and Madara's PS size and output.
Passerby said:
Can't they nuke Itachi with TBB Spam?
50% Kurama can only do 5 Continuous TBB at a barage, which Itachi's PS can probably tank, considering:
1. Rikudou Sasuke's PS basically withstood the blast of two TBB with moderate damage (referring to the fact that Rikudou PS Chidori equaled an RSM TBB). Scale it down and it becomes EMS Sasuke's PS receiving the same damage from a non-senjutsu enhanced BD, meaning it would take roughly 5 to destroy it. Now, add the fact that Itachi's PS would be above Sasuke's in base durability, plus..:
2. His PS would still have Yata equipped. Leaving all the hype aside, there's little doubt it'll greatly contribute to his PS' durability.
There's always FBD, but I'm confident Itachi's PS can withstand that too, though that's some serious speculation here. I'm also not sure about the damage he could do with a supersized Totsuka, though it's probably above EMS Sasuke's DC.
Either way, he can probably beat BM Naruto, though still loses to BM Minato.