Are we not over the whole Auba playing central thing?
Auba at cf means he gets smashed around by CBS all game. Do we not count how OFTEN laca is on the floor. It also means he is back to goal. Look at how often he gets the chance to run in behind from outside to in on the left and look at how many goals he scores.
With both Saka and Tierney playing they occupy the left leaving Auba to move inside. I would keep him on the left but buy a centre forward who can occupy 2 defenders leaving more space for Auba. Someone who can also win all the aerial duels allowing Auba to run onto them. I would also buy a central midfielder who can cover the left side.
Think about a 30 year old Ronaldo in the late stages of his Madrid career. Still played on the left, but they built a team to accommodate his defensive work.
Or just keep what we have and buy like two really good midfielders. Laca could probably still do a decent enough impression of the Benzema role in the system you mention.
You'd probably only sell Laca if you got a really good offer you could use to reinvest, and if you could get another striker cheaply - Jovic on loan for example. Otherwise you're just selling Laca to fund a new striker and you've got nothing to improve the midfield with.