MR AntiFun... Can make option Always Win Gwent???
Why would you want to take the only fun thing from gwent away, which is playing for the win? Just go around the world, buy all the cards possible from vendors and do the gwent missions that shows people who give legendary cards for prizes. Their decks are usually very easy to win and you get very good legendary cards that can single handedly win you the matches.
That's like having a button in trainer that says "Automatically win the game and roll the end credits".
Even somebody who uses cheats for a game can't possibly want to beat the game with a single press of a button. There is an adventure to be had in Witcher 3, those who only want to experience the story without any extra grind and such, usually use trainers for the fights and play the game through the dialogue choices instead of mashing the attack button.
Also they make it possible to use gear that you want, most of the time for visual purposes only.
But yeah, please play the gwent at least. Automatically winning the gwent matches is the same as never playing gwent at all. Sure you can create a full collection of legendary cards but there is no opponents left to try the deck of yours if you just pressed one button to win all of them.