It's very possible that the Straw Hats get some help.
But of all the fights the one that I think will really needs some help is Franky.
Jinbe is insanely strong, even facing off with the strongest Tobi Roppo and his subordinates, he should be capable of defeating them alone.
Robin and Brook fighting together and defeating Black Maria isn't impossible in my opinion. Especially considering the fact that Brook ice abilities are effective against her webs.
Nami and Usopp in a straight 2 vs 2 fight they don't stand any chance against Ulti and Page One (The result is what happened in chap. 995). However with the help of Tama controlling an army of Gifters and Headliners things are a lot different. I think if they make Page One and Ulti fight an entire army of Smile users, it will leave those two very injured and tired while Usopp and Nami prepare some kind of trap to give the final blow. Now with Tama there, it's no longer impossible to defeat the two Tobi Roppo.
Franky is the only one I'm not confident that could defeat Sasaki alone. I think Sasaki is the 2nd strongest Tobi Roppo, and probably around equal in strength to Snack or Perospero from the Big Mom crew, he should be really powerful. For example I think Sasaki should be equal or stronger than Vergo (Vergo is someone that defeated Smoker).
My ideal scenario would be when Sasaki goes 100% (hybrid form) and starts destroying the Shogun, Franky would try to defeat him by self-destructive the Shogun. It wouldn't work but would leave Sasaki very injure, and then Sasaki will start beating Franky, but either Kid crew (Heat, Wire, and the rest) will save him and team up with him to finish off Sasaki, or Yamato will save him and then she will defeat Sasaki alone.