Nine tails has nothing to do with Susano'o.
If you can't stabilze PS then you just can't use it. There's no requirement for stabilizing.
there is a requirement but he seems to be ignoring it
Well Madara nor Sasuke struggled with stabilizing it, so if there was a requirement, then he would've made it apparent by having them bring out PS only to have it not stabilize then make it clear that something was not right with the user, hence a requirement.
He never made any such notion, so any type of requirement is meaningless at this point
Its the EMS
and indra was always a freak of nature.
But do you see where I'm coming from?
If anything, PS is unique to Indra and his chakra.