In ETC mode you'd just about get away with it with a small crop. If the OP wanted servo zoom as he's described though, he'd have to go for old B4 ENG lenses with an outboard 12V supply to drive it. You'd have to be quite mad to do something like that though. Like this weirdo attaching an Angenieux ENG lens to his GX80 and lashing a Sony battery to it. Oh hang on..... Thats mine