Theoretically, selling vinicius Junior to buy a striker and make kylian mbappé to play his natural wing which happens to be where vinicius junior is strongly occupying now is a good option. But in practice it is very very risky. I mean there is no club that is rich enough which will have someone like vinicius junior who is considered the best player in the world now and selling him just to make some unrealistic experiments.
They have already seen the gambling that Ancelotti did how it is playing out. There was actually no need to bringing kylian mbappé when vinicius Junior is there. But if your recommendation is taken by Real Madrid, it is a 50/50 thing. It could turn out to be the solution to Real Madrid problem or it could worsen it. There is possibility that it will worsen the problem than to redeem it because kylian mbappé will tend to be the new king which other players might disagree with him.