Could we? Who?
If we want to bring in a first choice centre-back, he's got to be better in some aspect than (and broadly level in others with) Dias and/or Stones. I'm not saying that's impossible (I love both of them but accept that no-one is perfect) but it does seem a pretty small market.
Or we could bring in someone who accepts his starting position is behind those two, who knows that with injuries and suspensions and the amount of games we play and Pep's fondness for rotation, he will get a reasonable amount of gametime and a chance to fight for that starting position, but he's going to have to compete with a solid, reliable and improving Nathan Aké for it. But would someone who fits that description be better than Laporte?