Are you too dense to understand BZ was literally madar's will kishi just had to change his mind (an asspull) to use madara's will as his enemy, not even Aizen can backstab madara, because no one will expect his will to betray him/herHe is too strong yet a fodder like black Zetsu soloed him. In order to defeat Aizen Ichigo had to go to his strongest form which would have caused him to lose his soul repear powers.
If Madera lost to 8 Gates Gai that moment could have been replicated.