Something I noticed after a re-watch of 1st half (which I find makes gives me a stress-free way to look at the game) about our much hated Rodri-Gundogan double pivot and why it will stay permanently
1) Rodri typically played deeper than Gundogan when needed and would actually play between the CBs many times, Gundogan almost never did this, this was the clear role for Rodri, and Gundogan had alot more freedom to playmake. I think these roles perfectly suited both of them and created a kind of 3-1 shape at the back to build play from.
2) It served the purpose of allowing our fullbacks to provide width, because Gundogan and Rodri would drop to the left or right side respectively. And while Mendy was more threatening than Walker, just the simple act of having Walker out wide meant we stretched the pitch giving our forwards more space. Now Walker still played inverted for many moments with Mendy wide so it wasn't strict in that sense, but usually when this happens I found it funny to see KdB basically playing as a RB to cover him. I think the days of wingers giving us width is gone due to our players preferences, and while I think some people may prefer wingers for width over fullbacks, I think Pep did this to solve another problem
3) The David Silva problem, the player operating between spaces, it seems like from Pep's view, the best way to accomodate this is to play inverted wingers play between the lines (Ferran and Mahrez), and I think it was quite successful. This is also why we will see Foden constantly subbing on for the Wingers, because he can somewhat play this role for us. The problem might be Sterling who I think is the weakest of the 4 wingers in playing between the lines, perhaps the best role is for him to rotate in the striker positions (for example I could see Sterling and Foden up, instead of Jesus and KdB for rotation).
4) The 4th thing that the double pivot provides is KdB freedom, KdB was basically a striker for large portions in this game, very often I saw him even higher than Jesus. It's clear Pep is giving him the "Messi role" of just be wherever your needed, but unlike Messi, KdB isn't lazy and works on his defensive duties, and with Jesus we very often defended in a 442 when we lost the ball ala Atletico Madrid.