Natus has poison resistance but that shouldn't stop Sasori's poison from at least paralyzing his body
Gray's ice gets shattered by Sasori's cave busting iron sand
Natsu's flame gets blocked by iron sand
Can Natsu resist paralysis?
Current Natsu and Gray should win this fairly. Natsu's at least a town buster and Gray should be weaker but not much.
Natsu isn't a town buster.
Unless someone can prove that Natsu can resist paralysis they both die.
They won't even get passed Hiruko. Sasori can even control people with his strings.
There is a reason why more people say Kakuzu does better against Sasori. It's because Sasori doesn't do well against large scale attacks especially large scale projectile range ones.
Guess Natsu falls in?
Gray's freezing range doesn't help either.
Only potential threat is poison scratching.
Sasori can control them with threads and make them attack each other or use them to hold them still and poison them.
They're not beating Sasori.
And Natsu summons fire all around.
Gray is worse because he can freeze it although he is more effective using his hands for it.
Also again, Sasori does not do well against large scale attacks. Only his 3rd Kazekage is a threat.
A simple Base form Roar destroys hiruko.
The poison still gets burn away, like in the fight with Cobra, since it don't paralyze his magic. Natsu still have control over his flames, that fire guy from Phantom Lord try to control the flames and fail (so controlling his body will not work for Sasori)
Edit: I should really check for typos before posting :)