In this economy, even under the notion of player exchanges (Although quite honestly, if Atalanta want Perin bad enough, just sell him) , we would be getting a 26 year old guy whose ceiling may have already been reached, or close to being reached for 35 million.
To me, it would be better to take the money from the Perin sale (Let's assume 15 million), add ANOTHER 15 million and try to get Reguilon, who despite 3 years younger, is miles ahead of him as a LB.
Younger, cheaper, better contract (Not having played at all in Italy), and a player who can make you better now and in the future.
I just see this, and De Paul, as incremental improvements, with no concern for the long game.