Dude first of all Kanoha has enough intel about the uchiha fighting style for jariya to walk into a Tsukuyomi. Plus u don't even know if Itachi is power full enough to bring 3 sage under his genjutsu or if he even can do all three. Plus the other sage could act like Genjutsu protection disturbing Jariya's Chakra if needed. With Natural energy Jariya's chakra is stronger can itachi control that.
About the Amatrasu
we can all agree sasuke is more skilled in the use of Amatrasu than Itachi. So in the fight with Riakage why didn't sasuke simply stare at him and burn him up? Well it was because Riakage was to fast, the only reason Riakage lost his arm is because he willingly touched sasuke's black flames. In sage mode Jariya is faster not as fast as Riakage but fast enough. Also Jariya already has knowledge of Amatarsu, enough to hold naruto from touching it and seal it away.
I remembered a dude gave me the same argument on how to beat susano. Well Jariya can use this Jutsu:
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Susano and itachi would be drawn into this and ink to their doom. The first time Jariya used it it was weak because he was poisoned, he claimed had it not been for that he would of submerged the whole snake. Picture it now in sage mode total change of landscape. Then he could use this jutsu to finish him of:
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how is itachi going to walk on ground that is not there and doge that wave of flaming wind powered oil while still using susano? He will have to deactivate susano and when he does total pwnage will take place.