Oh . I think I get it the beast themselves, I don't think that they are aware that the 1-9 tailed beast is actually that SAME 10 tail beast. Sure they are called tailed beast but the ten tailed they fought was under specific control of Kagugya while the supposed tailed beast out int he world now have been imprisoned.There is nothing to say that they are the same or even part of Kaguya forces and with any history lesson that Ranma might deign to pay attention to, Kaguya does not even rule anymore.
Then of course there is Ranma herself (himself in the mindscape) Thinking from Ranma perspective why would Ranma want to ally with them to kill these beast that's taken care of? To Ranma chakra could be use for good or bad and is no different then ki in terms of who wields it. So in my opinion there really is no point in her trying to erase something that has been a part of everybody lives for over a thousand years. Ranma is not a hero , just a squirrel in the world trying to get by, doesn't even have any real loyalty toward anyone but Tsunade and Shizune. Live and let live, there is no major bad guy that Ranma is aware of at the moment , at least not yet that has gotten on Ranma radar.
Not Akatsuki, not Ochimaru, worse Ranma ever done and i'd show this in a flash back , is kill bandits and missing nin's which she is well aware of that done people wrong.
As for Tsunade and telling well, I don't mind spoiling since people don't read or reply in the fuku boards much anyway. Yep and Tsunade will quickly examine Ranma and call bullshit. ^_^ A lot of people are going off the assumption that the sealing arts is exactly like Naruto seals or similar enough but fail to remember that every other jinichuriki out there is sealed a different way. Even gara seal was different and sloppy from what I read, but Ranma's seal heh heh heh heh. Ahem. Yeah.

That's gonna be under the hat for a while BUT again the hint to that answer is all throughout the first five chapter.
When I revealed it and people go back to read it , it would be like "Oh yeah! why did I miss that!"