#1 - Philippe Coutinho:
Yes, we all know that Barcelona tried absolutely everything possible in order to acquire the services of Philippe Coutinho, but that does not prevent him from featuring on this list at first spot. The Brazilian has reinvented his game from left winger (or wide-play-maker, for more precision) to a creative force in central midfield.
Liverpool and Brazil national team managers, Jurgen Klopp and Tite have both used him as a midfielder in the last couple of games, and the 25-year old has impressed more than ever, following this change. With Ousmane Dembélé picking up an injury that could keep him on the sidelines for up to 3 months, Barça badly wished they could rely on Coutinho's brilliance in that wide position, as he would have certainly been an upgrade over what they currently have in Gerard Deulofeu.
The Liverpool star was involved in a total of 27 goals for both club and country last season (17 goals and 10 assists), which proves just how decisive he can be in the final third. So whether they used him on the left or in the Iniesta role, Coutinho would have still done the job. Andrès is a couple of months away from reaching 34 years of age, and with the club failing to secure a Xavi replacement, they would certainly not want to waste another opportunity to secure Iniesta's.
For all these reasons, Coutinho would have been the most important signing. And if there was any doubt about his ability to operate in midfield, we leave you with this video so you can watch and judge for yourself.