Just don't see them beating all 5 Kage leveled opponent at the same time. I may be wrong...Gai vs Onoki/Ay would be a tough fight but Gai wins that fight. However, Kakashi vs Tsunade, Mei and Gaara won't be easy since Mei easily alters his vision and giving the location, Gaara's sand would be terrible for Kakashi especially with the inability to sense while Gaara can sense him via sand. In the mist, this would happen:
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Kakashi can Kumai himself out of it but how long in the mist? When Gai is elsewhere battling Ay/Onoki? Onoki can also take advantage if distractions and use Jinton from above.
The only way I see Gai and Kakashi winning is if they stick together at all times like they did when battling the V2 Jins....Though I doubt them winning this fight considering their opponents. 5 Kage leveled opponents isn't easy. Gai is fast and powerful, so is Kakashi...but the number of powerful opponents is enough to take them down due to Onoki especially.