-Katon that pretty much covers the whole entire battlefield, one that he isn't evading nor is he countering or surviving without Orochimaru's abilities.
-Gunbai can pretty much tank all of his attacks, and if he gets a good hit, it'll bisect him as it easily cut through God Tree's branches.
Madara would destroy 3-Tomoe Sasuke, add in the curse seal, and Sasuke stands more of a chance, but every time he gets hit with Katon he'd need to use Oral Rebirth, cause he definitely isn't evading it, and as Itachi states,
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so he isn't using it more than 5 times at the very very best.
Gunbai would still tank all his attacks just like they would without Curse Mark.
Now this is with summonings restricted, if we do this with them unrestricted, Madara would simply summon Kyuubi and that'd be GG.