I want to laugh at the ones who claimed Madara's brother was in the casket. First what older brother fears their little brother LMAFFO, I'm sure the reason as to why Madara was the leader was because he was the older brother and like most older brothers kicked his younger brothers ass time to time. Second if some kid were to resurrect my younger brother's dead body I wouldn't sit their and say for that you can join, I would kick the Orouchimaru out his ass.
Kabuto could have brought back the real Madara maybe the real Madara can stop the impostor or if Kabuto brought the real Madra to the alliance they would get bold and attack.
As for kabuto his new power is great. With Oro's regenerating powers and his own medical powers he can take almost any attack. Oro has the greatest snake jutsus as seen when he faced the 4tails Naruto. Kabuto also has Oro's endurance and the white snake ability so he can recover from a battle like Naruto, he can have two full scale battles on the same day. His chakra levels should have increased too. Kabuto still wouldn't stand a match against Naruto sage mode or rikudou mode but edo tensei would increase his power level.