Kabuto said that with the power he created (Edo Madara) he could now touch a "fragment" of the sage's power. That by itself is massive hype. Though Kabuto probably never saw what the Sage could really do, perhaps he isn't a reliable source. Considering that not every Uchiha or Senju are necessarily equal in power, perhaps the Sage's Uchiha and Senju along with his Rinnegan are on an entirely different level. COAT is a specific Yin-Yang Release that creates things from nothingness. Just because he has some of the things the Sage had, it doesn't mean he's as good at using those things at the level of the Sage. Perhaps he does have Yin-Yang Release but it doesn't automatically mean that he knows how to use it. He did show great skill with Yin Release and Yang Release through his clones but what if that skill still wasn't good enough? And he needs to learn how to use Yin-Yang Release altogether.To use COAT, he has to know how to create a form from nothingness and another feat to breathe life into that form. Yin-Yang.
We only know he managed to subdue the Juubi and used COAT to distribute its chakra into the 9 tailed beasts. After that, he created the moon with the Juubi inside it. Whether he used the chakra of the Juubi is still unknown.
With COAT he could probably create copies of Madara to further aid him in battle. Perhaps clones of himself or the Juubi. Though he might have to distribute chakra into those forms so perhaps they would be weaker or maybe they become their own beings with whatever amount of chakra the Sage wants to make them with. To me, COAT is his main hype. Aside from the probability of him creating more techniques to fit the situation.
