The possible signing of Griezmann goes hand in hand with Bakayoko imo. We are talking about a powerful, athletic midfielder who is very mobile. He can certainly play in a two with Pogba next to him and Griezmann just in front. If we replace Carrick with a similar sort of DLP, then I think you need to keep two midfielders in front of him, with Pogba in the more advanced role as we've seen recently.
Let's not forget that Carrick used to be very mobile. Much more than people remember. I think the potential Bakayoko signing hints at a more attacking line up in the long term.
This is how I see us lining up potentially next season:
Goalkeeper: De Gea
Defense: mourinho will only play with one attacking fullback imo. So Shaw and Valencia will probably trade off, assuming the former makes it here long term.
E.g. Valencia, Jones, Bailly, Blind
Or Lindelof, Jones, Bailly, Shaw
Not sure about the Semedo link. Think Darmian is toast, and possibly Rojo too (despite his recent resurgence). If he stays fit, I think Jones picks himself. With a nearly a full season back to back, he could reach great heights.
Midfield: I think Jose's switch to 4-3-3 is a reflection of his personnel, rather than his preferred system. I think he's also aware that the team doesn't score enough goals yet; and as we've heard multiple times, playing style and risk are high priorities. So if we can get Griezmann and Bakayoko, I think we'll revert to a 4-2-3-1 for a lot of games. He'll offset that by making sure his wingers track back a lot.
This is the biggest threat to Martial. Adapting to instructions. And unlike most, I'm not convinced Rooney will leave. I think Mourinho likes him on the left because his work rate is still phenomenal.
I'd expect Bakayoko and Pogba for the 2 pivots, and Griezmann as the 10. With Carrick, Herrera and Mata as backup. Reverting to the recent 4-3-3 for big matches.
Out wide, Martial, Mkhitaryan, Lingard and Rooney competing for 4 spots.
Up front, Ibra and Rashford.
All of Darmian, Schneiderlin, Schweinsteiger, Young, Depay, and Fellaini will leave I expect. And I would say the futures of Rojo, Shaw and Smalling are currently in the balance to differing degrees; although far from certain to leave.