A puppet can't be put under genjustu? Thats like saying a rock can be put under Tsukuyomi..
..a puppet without brain and vocal cords shouldn't be able to speak and think either, yet Sasori can. That kind of logic just doesn't always work in Naruto. The organic container in his chest contains Chakra, his humanity, hence Genjutsu works on him. Even if it wouldn't, Itachi has enough techniques up his sleeve to kill Sasori.
The only living part of Sasori is the scroll in his chest. So, are you saying, if Itachi looks at the scroll then Sasori's under genjustu? Because that is were Sasori's mind is kept.
Im still not convinced that visual genjustu will work on Sasori. Evan still, you are right that Itachi does have many other techniques. In my opinion Susanoo would be almost impossible for Sasori to counter...
And what is this that visual illusions used with a Sharingan and normal ones vary in? The former are only way harder to break. The only illusion that's most likely useless is Tsukuyomi, that much I agree, since Sasori doesn't feel pain - even though I'm not certain if that includes his organic container.
