Pretty ambivalent on Hakimi. He's a speed merchant who has done very well in a defensively atrocious Serie A, but at the price quoted we have much more pressing needs. The main reason is that it is based on the assumption that Tuchel is going to stick with 3-at-the-back formations; historically, he is a notorious formation tweaker. I'm not sold on his ability on the ball either; Reece James is one of the best crossers/passers in the team already, and is able to hit hard, first-time crosses, whereas Hakimi has spent a season with all the time in the world on the ball to pick out the towering Lukaku.
In saying that, Hakimi is one of the fastest players in the world and in the EPL where teams need to counter-attack quickly, that means a lot. James and especially Chilwell are fast, but Hakimi's speed is a notch above and maybe Tuchel's thinking is that he could be developed into a 2-in-1 player who is reliably able to support counter-attacks and defense. In 3-at-the-back he's a wingback, and in a 4-at-the-back he's an orthodox winger.