I'm not going through the whole thread, but I think you guys are simulating the fight to your favor. Fights never go in such simple matters.
Chibaku Tensei COULD fail because water can seep even into the ground, and to an extent, rock itself. And there ARE cracks in the ground in Chibaku Tensei.
For Bansho Ten'in, Kabuto COULD potentially use snakes to root him to the ground.
For Shinra Tensei, he could do the same as Bansho Ten'in.
Can these happen? Yes. Does it mean they will? No! But he has counters if he needs it.
I personally think they have a chance to kill each other, or Kabuto wins. Sage Mode took out FOUR bodies of Pain from Jiraiya (Animal Path twice). Kabuto has this, plus intelligence to figure out his abilities.
He can use jutsu that disables Pains eyes. Not only ONE Pain, but all six at once.