You say it as if Kabuto will summon all his edo's and have them huddled together, standing around...doing nothing.
Edo Madara + Kabuto can take on Juubito, Edo Madara + Edo Kages + Kabuto easily solo.
Have the 5 kages rush Obito along with Madara, then Kabuto can trap Juubito (sound 4 ninja) Tayuya's chains of fantasia, immobilizing him completely. Kabuto then finishes him off in anyway he wants.
You can try to say that Edo Madara can break out of edo tensei at anytime, but that's situational and debatable on its own. If there's no reason for Madara to release himself and he has free movement, he shouldn't.