I think so. Marchisio would be a fulltime CM, like Lemina.
His salaries are so high that it would equal a Andre Gomes like transfer (bigger fee, but much lower salaries).
I think they will make a big signing in the mid, but are looking for the best opportunity, in all positions. A DM would free Marchisio to rotate with Khedira.
A CM would immediately fight Khedira for the position, and a big signing AM would revamp the whole team (less likely choice IMO), making it almost mandatory that the scheme goes to a 4 men defense. Marotta's priority is probably a guy just like Pjanic - creative CM and AM at the same time.
But Gomes definitely looks like a realistic option, and I'd love to have him as the CM.