Probably be pragmatic and prey on City`s weaknesses. Main one being mental liability. I bet Pep was thrilled when he saw what Carlo "prepared". Probably died of laughter also.
That being said. Formation / system wise, it should have been 4 man midfield with two forwards upfront. Sit deeper and compact and when winning possession of the ball, use fast break attacks and counters. Player wise. Alaba should have played LB. Rudiger should have started. Touchu and Camavinga should have played as double pivot, with Valverde playing wide midfielder. The only question being who should be fourth one. Usually Modrić. But given he was recently injured and probably still not being anywhere near 100%, i would have opted for Ceballos. Upfront, Vini and Rodrygo.
Decisions such as going with three forwards. Thinking that two geriatrics and comatose Valverde, will answer City. Also playing LB as CB and CM as LB, and benching best CB of the previous game who pocketed Haaland... I mean. That is not just an amateur hour, but completely inexplicable for a mediocre coach let alone top one. Basically it is as if Theoden and Aragorn would put their troops ( archers ) in front of Helms deep walls, to face 10k orcs.
Step one: sack Carlo.
Step two: quality coach with capacity to say goodbye to "amigos".
Step three: left back - Miguel for "free", RB - absolutely crucial position. CM - Bellingham, RW - i would gladly take Bernardo Silva. Striker. I would also consider CB - Gvardiol, considering Militao is to brainfarty for my taste.