Interesting fight.
I actually don't think Jiraiya'll manage to stall and activate Sennin Mode in a location like this, considering the opposing team possesses both Minato and Ei, two of the fastest shinobi in this manga. Unlike in Amegakure, where Ero Sennin fought Pein, this setting doesn't favour the kind of guerrilla tactics which would enable him to stall and gather natural energy. If the intent is to kill, I expect either Yondaime to immediately press Jiraiya and stop him from activating Sennin Mode - particularly Minato, as he's signed a contract with the toads and was also a former student of Jiraiya's. He should be aware of what his former Sensei is capable of. Tsunade may find herself in a similar situation. Employing her Byakugō would allow her to tank much of Team Kage's blows, but it wouldn't give her the speed or agility needed to take out the two speedsters. It would be helpful if she had a single Jutsu with a very large AoE, but she doesn't.
Hiruzen doesn't have the feats to compete at this level, especially since the Shiki Fūjin has been restricted. Though with Enma, he may prove deadly in CQC against the likes of Mei. With Orochimaru backing him up, I can see the Mizukage being pressured out of the game. She could use her Kōmu to keep her distance, but this raises the issue of collateral damage. Granted, Hiruzen's odor based tracking skills are impressive, but a well timed Yōkai no Jutsu (Melting Apparition Technique) from the Mizukage might be enough to catch the Old man napping. It won't be enough to best Orochimaru, however. He's superior is practically all aspects, and would likely kill her with the Kusanagi no Tsurugi.
The Yondaime Kazekage isn't well rated amongst the majority, but he could prove useful in dealing with the likes of Manda and Katsuyu. His Gold Dust was able to subdue even the Shukaku, and so displacing and crushing the Sannin's summons doesn't seem out of the question. With Jiton, the Kazekage can also manipulate Minato's kunai, and hence, make the latter's Hiraishin even more unpredictable.
The Kage's main issue is permanently putting away Tsunade and Orochimaru. In this scenario, I think Jiraiya, Mei and Hiruzen will all die relatively quickly. Of course, with Edo Tensei you'd favour Team Sannin - but with only the featless Nidaime able to be summoned, I haven't factored in its usage. Exhausting Orochimaru's Kawarimi with frequent, robust techniques would most likely lead to success. The Godaime won't recover from decapitation or a crushed skull either. If the Kage's fail to successfully deal with the summons or defeat Orochimaru before the likes of Yamata no Orochi are brought into play, i'd favour the Sannin. If they go for the jugular right from the off, I think they can take it.
