here, this is a better translation :
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Sasuke observing naruto.
"so this is what he's like when he's got control over the kyuubi chakra... "
This suggests sasuke noticed much more than what tsunade noticed, an advantage of being a sharingan user.
Now let me show you what tsunade said :
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It is clear she just saw the change in naruto which a normal person can see.
That makes more sense to you but that does not necessarily mean that it is the right thing.
You don't have anything to prove your argument and no kakashi-obito connection is not same as what you are saying.
Kakashi at least have one eye but in madara's case, he is completely blind.
Also, if something like that was possible, why only susano could be used by madara and not all the rinnegan techniques.
And you didn't say anything about how itachi was able to use susano without activating sharingan