The battle will start with Mei using Hidden Mist Jutsu while Tsunade pumps her up full of chakra. While they do this, Onoki make a rock clone to get in a backpack combo with Ay and lightens Gaara's gourd sand. Hidden Mist blocks Sasuke's line of sight so he can't be sniping characters left and right with Amaterasu, nor is genjutsu happening when eye contact will be impeded by Mei's mist; Gaara has sand sensing to operate without vision; Ay is too fast to get caught in genjutsu; a Katsuyu clone on Tsunade's shoulder can break her out of genjutsu.
With that being said, Sasuke needs to use at least a V3 Susanoo for the bulk portion of the battle since Ay can bust V2 Susanoo, and Sasuke needs V3 to access Susanoo arrows (he needs V4 to access enton orb.) Gaara can create massive sand arms out from the desert sand to grab legged Susanoo's legs and restrain its movement. Lightened Ay can buy the Gokage enough time for Onoki and Tsunade to prep his super jinton. Gaara will be next to Onoki so his lightened sand can intercept Amaterasu easily so it cannot disrupt its prep. Susanoo slashes can be tanked by Gaara's sand [
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]. Susanoo arrows are the only thing that could possibly stop the jinton from happening but seeing how Gaara can go offensive and
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while Tsunade charges Onoki full of chakra and he casts super jinton, it's unlikely he can do this especially with Ay acting as a distraction and Mei's mist impeding vision (BTW Madara's senjutsu enhanced V3 Susanoo would be around EMS Sasuke's V4 in terms of physical strength and durability.)
Gokage win mid-high difficulty with full intel.