I think I read this somewhere previously but it came up again in a game last night.. Once a Mad Scientists invents the Bio charged neutraliser he will be equipped with a weapon which he cannot trade (Card wording: This dude is a stud. This card cannot be traded, and is not affected by other players' card effects.)... SO... if he now invents another weapon intended for another dude then he will have two weapons after the shoppin' play so he would have to discard one of the two... presumably the bio charged neutraliser otherwise there would have been no point inventing another weapon only to discard it!
So neither of us knew and we agreed my opponent could invent another weapon provided he immediately traded it with his next play... Having researched I think we were wrong but it does make the 'cost' of the bio charged neutraliser high given it effectively disables a mad scientist from inventing further weapons..
Looking to confirm that my understanding is correct.