On a hit to the cybernetic part. The paragraph is referring to a hit on the enhancement, not the whole target.

Either way, the bad guy would add a black to target at the "legs", but because he was aiming he would get a blue... it would actually still edge into his favor as the blue has better results then the black. And this still doesn't explain how aiming at one leg, would knock out both (per the example). In addition it's only an argument for biologicals, as droids conduct electricity, thus why ion works on them in the first place.

Can't do the Aim you are describing, gotta pick, boost Aim or specific item Aim.

That is up to the GM if they install those things. If they let them, then apparently it wasn't OP in their opinion or they wouldn't have let them install them at all. There is nothing written in the book that says a GM has to allow players to install or buy anything they want to as if they're ordering items from Amazon. That's just a lack of imagination and story control on the part of the GM.

Or one that didn't read up on how they were supposed to work. Or one whose players are trying to pull the wool over their eyes. Etc... If it is your game run it how ever you wish.

Look, I'm just saying what the book says. I can't change that, I didn't write it. As I've said, run it how you wish. I would ask myself why I was being so defensive about it. Kinda sounds like it affects a character of yours and you would rather it didn't. Not saying that is what is happening, but it is how it is coming off.

The book does not say if you just hit a target cybernetics stop working. The sentence is "If hit by weapons that normally affect droids only, the cybernetic enhancement stops working for the remainder of the encounter or until it is repaired."

This is a conditional sentence with an antecedent and a consequent with cybernetic enhancement as the subject of the sentence. The 'If hit by' portion of the sentence is the antecedent and the 'stops functioning for the encounter/repaired' is the consequent. The sentence is specifically and very clearly saying if the enhancement itself is struck what occurs.