De Bruyne , Silva, and Nasri are not CM's they are CAMs. Sane and Nolito are wide men/forwards.
Which again only leaves you with a currently injured Gundogan. Fernandinho who is obviously good enough but can't play every game and then Fernando and Delph who are both not good enough.
I'm not even going to count Yaya as his legs have gone and he will not fit in to the Guardiola system
We are talking about different things entirely. The premise that we need 2 more CMs is predicated on the argument of who is or isn't good enough ( just as you've outlined above.) However, my claims are based simply in logistics. It's acnumbers game. Currently we have 8 players who are not considered Wingers, Strikers, or defenders. I listed those 8 above.
All 8 invariably will slot in to one of 3 positions in the middle. Even if you are right that they are not good enough (an opinion I somewhat disagree with) it still doesn't change the fact we have to move at least 2 to make room for a new 2.
Gundogan, Silva, Fernando, Delph, DeBryune, and Dihno seem definitely safe from reports. Which means you really already have the 6 (I.E starters and Backups) for all positions. True some may be moved elsewhere (Dihno RB, Delph LB) which will then open 2 spots. But to even fill those 2 spots both Yaya and Nasri will have to be moved.
Right now, that is proving difficult. Assuming we are able to move Yaya and Nasri, redeploy Delph and Dihno, then we can start talking about getting 2 CMs. As it stands now, getting 1 more will be hard enough.
Also redeploying Delph and Dihno will end any meaningful search for fullbacks.