I really don't know how to imagine group fights lol .. But it seems you believe the Kage's win? Can you post how? And Shisui is featless lol.. why add him?
I'd imagine Shisui as the first Itachi before Itachi took Shisui's whole swag.
So personally, I'd say he's basically another Itachi, but faster (due to his nickname) I guess?
Anyways, here's how I see it.
Hashirama and
Madara will make the first move and fight each other alone.
Because y'know, they love each other. They're pretty much equal so the fight will be long.
While they're busy,
Minato must keep
Obito busy or else Kages will definitely be in trouble.
KCM Minato vs Rinnegan Obito, I'd say Minato can pull this off. How long it takes is debatable, but it won't take long judging by the fact Minato has already marked Obito before and has experience fighting Kamui.
What's left is
Hiruzen, Tsunade, Kakashi, Tobirama vs Itachi, Sasuke, and Shisui.
Tobirama will play a major role in this because of his experience fighting Sharingan users all his life.
He also has access to the Bringer of Darkness technique + Flying Thunder God.
Hiruzen/Kakashi/Tsunade are a liability, but they can definitely help in some way, Kakashi being the most valuable asset due to Kamui and his expertise in using Shadow Clones.
I'm pretty sure they can keep fighting long enough until Minato comes to help, and when he does, the fight is pretty much over at this point. They'll kill Itachi/Sasuke/Shisui off and go on to help Hashirama finish off Madara.
The worst scenario is Tsunade/Hiruzen (maybe, Kakashi) dying against Itachi/Sasuke/Shisui and I see that as a major possibility.