The arguments seem to come hot-off-the-heels of last night. My feeling is that our performance was top drawer, but that doesn't mean we should be out on Sanchez. Pep alluded to as much in the post-match interview. Cover is needed for injuries, suspensions or just plain old loss of form. Sometimes KDB is off, sometimes it's Aguero, sometimes Sane and often Sterling. Behind them, is a wafer thin bench with little option available, particularly a match-winner who is arguably among the best in the PL like Sanchez.
His 26 goals and 13 assists this season is the best around, by a measure. He's proven at the highest level. He would improve us immeasurably and the issues of "keeping him or others happy" is for Pep to wrestle with. If he wants him, and he wants to come, then we should get him.
I mean, there could be £80-100m difference in price between Sanchez and Mbappe. With as many transfer targets as we have in other positions (GK, 2 LB, CB, 2 RB, DM etc) Sanchez would be the more realistic option by a measure.