Wait do you mean solo them all st once?!
I think if some of the....lesser...captains worked with and followed the actions of the older Captain they would win.
1. Shinsui and Jushiro were his students so they know him well.
2. Unohana was a woman so dangerous Yamamoto sought to bring her into the system instead of killing her off.
3. The plot nicely powered up Zaraki to secretly be a freaking monster
4. Byakuya and Mayuri posses keen intellect/combat skill
5. Toshiro and Soi Fon possess useful bankai despite their youth.
7. Kommomura's giant blade could provide a valued decoy.
8. Shinji messes with perception.
Finally Bankai for the uppers. We have yet to see Jushiro or Shinsui bankai, and seemingly anyone too close to Unohana melts to death. Mayuri poisons, and Byakuya had godly petal blades.