Here's a thought on the possible outcome at CAS.
1.Due process was not followed, specifically in Uefa's failure to address City's defence adequately.
2. The sanction is set aside.
3.Uefa must go back to the AC and properly consider that defence and reach a fresh conclusion.
I think that is quite likely.
With AC Milan, CAS ruled UEFA's punishment of a 2 year ban was way too much and sent it back to the Adjudicatory Chamber to go and come up with a sensible punishment. Then Milan fell out of the CL spots and accepted a ban in a deal with UEFA so they didn't have to play in the Europa.