Sell Alba for 60-80m and buy alaba for 60-80, doesnt sound too bad. Well never gonna happen, but it would be a step to a more independed messi-team. I now we all love those alba-messi moments, but have those to connected at all in champions league? The guy is heavily depending on workrate and speed, and is hitting his 30s - could be a nice pro-active move. We would be slightly worse off in la liga short term, better in champions leauge long and short term, and i think we would play more as a team with alaba > alba.
Alba has still been top 5 performing player this season, so we would take a gamble, which could pay off big time.
Dembele-------------Griezmann
---------------Messi
-------de Jong---------Arthur
-------------Sergio/rakitic
Alaba - Lenglet - De Ligt - Semedo