I don't really care if Courtois leaves.. Rip Real or PSG off and he can go if that's what he wants. There are many great young goalkeepers in the top leagues - Rico, Lafont, Alisson, Strakosha, Perin, Leno, etc etc.
I firmly believe that the goalkeepers role is not that important in modern football. Of course a good keeper can make a difference but the defense and the midfield is much more important. Barcelona were on their prime with Victor Valdes, Real won everything with Keylor Navas while MU struggles with De Gea.
I would be happy if Thibaut stayed as he is a great goallie but if we can sell him for good money and use that money to strenghten the midfield or defense then let it be. Keeping Kanté and Hazard would be much more important.