What we've seen is that ONE bijuu alone isn't enough. What we've also seen is that techniques rule supreme, right after eye powers. So depending on what Madara has up his sleeve by way of techniques, he may be able to use the Bijuu as a power source to fuel them, Like Kisame + Samehada uses their opponents chakra to fuel Kisame's techniques. I know Madara said that he doesn't have anywhere near the power he once had, but we don't specifically know what he's lacking compared to his former self. The bijuu might somehow make up for it, maybe even more than make up for it.

As for Danzou...just kill him off already.