EMS Sasuke can focus on Mei, Tsunade, and A at the beginning of the fight, and can monitor Onoki's Jinton along with Gaara's movements. Tsunade and Mei are taken out fairly early in the battle with two enton arrows. Remember, Sasuke can use Enton arrows and Magatamas simultaneously now, as his Sussano has three hands.
A, along with any Taijutsu user is literally useless here. Sasuke can coat his Sussano with Kakasgtsuchi and create a wall of Amaterasu from Enton projectiles as he did so during his fight with Kabuto. This will kill any Taijutsu users who even try to do this. He can use Magatamas to busy Gaara and keep his eye on Onoki. He can even try and put him under Genjutsu. After Sasuke is done with Mei and Tsunade, he can shower Gaara with Enton arrows and Magatamas. Gaara will be finished sooner or later. Or an Enton Sword cuts through his sand killing him.
Once Onoki decides to use Jinton, he uses Amaterasu to kill him in one go. All that is left is Gaara now, who is in a constant threat from all the enton projectiles lying on the battle field and can be utilized at Sasuke's whim to create Amaterasu walls and projectile. In fact, Sasuke can create one around Gaara to limit his movement. If he tries to fly, he is put under the force of enton arrows that will go clean through his defense, as not only is his sand not fast enough to keep up with arrows that forced Danzo to use Izanagi and Kakashi to use Kamui. If He tries to penetrate his Susanoo - IF Onoki manages to lighten his sand that is - it's easily countered with Nagashi and Kusanagi, or even cut through easily with Chidori spear.
If A is still standing, then he can get taken out in so many different ways; genjutsu is one of them. Sasuke wins this mid-difference max as three of them - especially Mei and Tsunade - are easily picked off right from the start. Onoki's Golems will prove to be as zero distractions as Sharingan can give colour to chakra whether it's underground - like in Deidara fight - or behind an object - as in Kabuto fight - henceforth, his distractions won't work against these opponents at all. Onoki's best bet is to prepare a jinton, and that is a fatally sluggish technique compared to Amaterasu and arrows. He's taken out there and then if he tries.
Mei's Lava attack couldn't penetrate ribcage Susano'o; she isn't accomplishing anything here. The fight then boils down to Hashirama and Edo Madara. Edo Madara is Edo after all, but I would like I withhold my opinion on this this until more is revealed, but Sasuke clearly wins against the Kages as two of them are literally one-shotted right at the beginning and A, being a close range fighter is useless here, so the actual battle is with Gaara and Onoki. With Tsunade out of the way, Onoki cannot prepare extremely large Jintons anyway, and any attempt on Gaara's part to pull Sasuke out after having his sand lightened is instantly negated with a single Nagashi.
