When it allowed a MS jutsu that could only be used every decade to being used in under 6 hours. When it made a chakra taxing Izanagi able to be used 10 times with no side affect what so ever on a man pass the age of 65. When it allows Obito to spam Kamui to to end and allow both madara and obito to control the Juubi itself. Plus SM in general places everything on an entirely different level. Plus the databook fact that the cells are alive btw. Anything else?
That's not up to reserves. If it was, don't you think KM Naruto had more than enough chakra to back that up? Uchiha and Senju had a deep connection that has proven to affect eyes. Also Obito's Mangekyo was never indicated to be bright. Kakashi got blind much later, so did probably Obito. Nevertheless, we don't know how blind he ever was.
The cells never granted HM, lol. If this was true, Madara wouldn't have had to literally suck the Senjutsu out of Hashirama.
None of your suggestions have basis. If cells did add chakra, it would have made characters like Yamato chakra monsters. But it didn't since he got really tired of making just few blocks of wooden houses.