Kishimoto was taking the context of "All Seeing Eye" to the extreme, and it can see heavily chakra only. To a certain point, there would be say an outline of clothes, yes. But no, they shouldn't be able to see dangly bits and whatnot, because it's a Doujutsu that sees the chakra system and the tenketsu as well when focused. Beyond that, if it ain't related to chakra, it can't be actually seen.
Weapons, pffft, if it ain't chakra as I said before, no go. Now, if the user has skill and talent, and can logically know that judging by the outlines and where the limb is, they should be able to realize a weapon is being grabbed. But no, hidden weapons are hidden even from the All Seeing Eye. For seeing through clothes, well, the chakra system is in the body so really, it's more like the clothes are not registering to the chakra seeing eyes, and are merely just outlines. Look at the fight between Naruto and Neji, he can see an outline of Naruto's clothes, but that's it.
>.> Byakugan ain't a peeping weapon, but it can be a medical tool. Make sure that baby's healthy chakra wise.