To be entirely honest, I'm not sure how I feel about the power of the ten tails entering the site. It's literally so overpowered that if you don't have it you lose.
I've pretty much already decided that what I'd get from hosting the 10 tails is
Infinite Chakra
Truth Seeking Balls
Two Kami level Ninjutsu I want to do
and 9 tails Chakra Mode/Sage Mode/whatever levels of power all the time.
I don't think we'd rp it being out in beast form like the mange did because then yeah it is stupidly strong. You would just need to do one Tenpenchi to kill every opponent without Izanagi, Kamui or Hozuki forms.
The only thing questionable I think is the Truth Seeking Balls. But I think it's all pretty fair if Akatsuki does manage to get all 9 bijuu and the Gedo Mazo that we can make the 10 tails. I'd be willing to make official rules for it before doing it in rp if we do amass all the proper Shinju ingredients.
I think it would be pretty asinine at this point to just say no 10 tails and remove Akatsuki's win condition. Especially considering how hard it will be to hold onto all 10 parts of the Shinju (9 beasts and a Mazo).