It all kinda depends on if we stick to wide fullbacks (double wide like now or maybe just 1 or none next season).
1) Wide fullbacks 4222/442 (diamond)
Anderson alone isn't enough, I count only a strong core of 20, but we are light at fullback.
While Nico O can be considered the backup at LB, its kinda fake depth because then we lost a midfielder depth, and if we only bring in Anderson for the departures of Bernie and Kova you can see the problem.
This is easily solved by buying another LB and RB (Nunes backup), or ideally 1 fullback who can cover both positions would be ideal to keep a strong core of 21.
The downsides I see here are trying to convince the CBs to accept sitting on the bench, because when fit, usually Pep doesn't like to rotate the backline as much as he does anywhere else.
2) 442 to 3412 (in possession)
One potential solution is to go to a back 3 in possession (still back 4 out of possession) by tilting 1 fullback wide and 1 winger wide, which in a coincidence also requires no more new fullbacks, but can use our younger CB depth like Reis and Alleyne who are likely more accepting of backup roles than Guehi/Gvardiol.
I wonder which of these 2 systems we use next season, very clearly we are using 1), but Im not entirely sure we will next season.