I'm not sure your numbers are accurate. Let's say they are. You want to replace our second highest earner with a player who will also earn a lot.What he makes and what he will cost the club are two different things.
Plus he doesn't make more than de jong.
De jong makes 25m per season, all in kimmich 18-20m.
De jong cost the club 30m per season.
Kimmich will be a free transfer who's sign on bonus isn't included in total cost.
So his cost on the box will just be 18m euros.
We bernal won't be ready for another 1.5-2 years
That amount of money should be for premium players. Kimmich has been on a steady decline now and will be 30 next year. In what way will he warrant those wages and a hefty sign on? He'd be what, 3-4th best CM in the squad?
Besides, Bernal looked very ready against the Liga teams he faced and Casado did well against Bayern. With two players with that kind of level it should be sufficient to rest the best of them while still being competitive.
Kimmich wouldn't even replace Casado/Bernal like for like, it would be like Frenkie, that he needs another balanced CM/DM next to him.