Willock seems best suited to a wide/outside CMR in a 433 alongside a playmaker type, rather than as either the AMC or AMR in our 4231, let alone as one of the 2 CM/DMs.
I'd keep both him and AMN for a switch to a 433 AND because they are both HG, rather than selling because we want to generate revenue/cash flow, and then need to replace them as HG. However it is this HG component that will likely see them sold, particularly now that we have failed to complete the purge regarding our senior players.
IMO our HG youngsters are going to pay the price for the failures of the last 2 summers in terms of both the squad purge and our financial restrictions/policy, and I suspect we will also see Arteta retain the 4231 as part of this domino effect as he will still not have the players he wants to play his 433 (not that I think we should be spending so specifically so as to give a rookie manager his preference to have both a left and right footed CBs.