I kind of like the idea because Mbappe is the left winger number one in my opinion and if he gets to play in his preferred position, Real Madrid would finally get the best of him. He has been playing in the center so many games, when he played for PSG he played there too sometimes, but it is not his best position. He will still score a higher number of goals, but he can't give the team as a whole what he could give them if he played in his favorite position. However, there will be big resistance I think from many of those who are either in charge there or negotiated the deals with Vinicius. It could be the right decision if they find the optimal striker.
It's true that Mbappe natural position is on the left wing, but I don't think Xabi Alonso would take a big risk by switching Vinicius to a center forward. Over time, I think Vinicius and Mbappe will develop the desired chemistry, they just need support and creativity from midfield to score more goals next season. In reality, Real Madrid attack doesn't have any major issues, their current weakness lies in defense.