If Liverpool really do sell Fabinho to Saudi Arabia for 40m and also get some kind of fee for Henderson, it seems like they could make a play for Caicedo instead of Lavia.
Liverpool seem to have the same issue as Chelsea in this situation: Lavia looks like a good prospect but are you really going to rely on him as your starting DM? He is 19-years-old, really raw, has never played more than 2500 minutes in a season, and his only first team experience has been with a side that didn't have the ball very much.
I think it would be kind of insane for Liverpool to trot out a Lavia, MacAllister, Szobo midfield next year. Not only is that changing the entire group but you've got one 19-year-old who has never played first team football for this kind of side, one 22-year-old who is new to the league completely, and then MacAllister who I rate highly but is really a complementary all rounder that will shine in a team that is otherwise functional but isn't going to drag the team along on his own.