I like McT further forward, he's a bit wasted in the Matic role because he's very good on the press for a young guy and isn't just good at breaking up play, he can also play a bit. Let's not get carried away though, we don't really know how good he is and realistically will he be top level? We'll only know in a few years. It's not even a case of needing to be WC, they can just be a good player and would immediately improve us.
Personally, I think we've always lacked someone like Doucoure who is more of CM/DM who can sit deep, cover and also get forward to contribute to attacking phases. They won't directly score or assist a ton but they'll be involved in a lot of attacking work. We were very easy to play through last year because I feel our CM core is well below average in terms of it's ability to recover the ball & transition into defensive shape. We were just a bit slow all round. Off the top of my head players like Gueye, Doucoure, Ndidi, maybe Rice although I'm not sold on him or Brozovic (who in my mind is what McT could become and is a v well balanced CM). Could also say Partey although I know nothing about him in honesty.