Looking at Bayern today, it reminded me of this thread.
See how smart Kimmich and Davies are used depending on where the wingers and midfielders are positioned.
If the wingers are wide and one of the midfielders make an attacking run, they go central and either act as a playmaker (Kimmich) or as a close passing option (Davis). By doing this they ensure that Bayern are able to continue to have the ball in the final third rather than pass it back to the central defenders and thus allowing the opposition to reorganize themselves. And if the wingers go central, they huge the touchline to make it more difficult for Barca to stay compact.
While this is not new and has been used by Guardiola for many years, this flexibility in movement and positioning among the players is a nightmare to defend against and press. And while having the passing and vision like Kimmich is a rarity to find among even the best midfielders, one does not have to be brilliant on the ball to be able to function as a passing option centrally, but one should be better than AWB, Shaw or Williams.
Another important factor that makes them able to do this (besides their ability in keeping the ball) is that they have two fast central defenders that are capable in 1v1 situations, a thing we sorely lack.
We have seen over the last 8-10 games that the opposition wants our fullbacks to have the ball and are actively protecting the middle of the pitch to stop PP and Bruno. Us going into next season with no fullbacks more able on the ball or a team incapable of utilizing our fullbacks better in the buildup, in the final third or in any situation where we are in possession would be negligence of a similar order to us not buying a midfielder last summer. Us having two fullbacks (or at least one) that are better on the ball, in the buildup and in the final third would help us more as a team than buying Sancho.