My thoughts (long post):
People are probably sharpening their pitchfork's as I type this comment, but I definitely think we should consider him as a Sané replacement. Neither Barca or Bayern has played to his strength's, so I reckon the world class player is still there
Pro's
1. He'd be very versatile in our system. Either of the left sided positions (offensive mid and inside forward) would suit his playstyle like a glove
2. Getting him would mean that we finally can put Sterling on the right again. Everyone and their Granny knows when he's gonna cut in, which has forced him to use his left foot
3. When he scores every Liverpool fans would probably feel like forking out their fucking eyeballs
Con's
1. If he plays LW the left side of our team would consist of fucking turtles. Neither Mendy, Foden or Coutinho are known for their pace.
2. If he plays offensive mid he'll take Foden's place
The problem with a Sané replacement is that his position is practically extinct at the top level which means that a. We have to get someone with another playstyle like Coutinho or b. Convert an left footed inside winger to a left wing like we did with Sané
Oh, and before anyone says Leon Bailey, he'll never be NEAR city quality. Stagnated for years and wildly inconsistent which means he's glued to the Leverkusen bench. Pep would probably play himself or Gundogan at left wing before Bailey
Tl;dr: Coutinho is a good and versatile fit for us. Sterling would move to the right, but left side might be too slow with Coutinho as a winger. Him as an 8 might decrease Foden's minutes. No real Sané replacement on the market because every left footed winger plays on the right, so we'll have to settle for a different player type or convert a right winger like we did with Sané. Bailey is a similar player but is wank