Are you arguing with someone else? I was simply pointing out that Ake wasn't really a stand in - he's not first choice in any position, but is a very solid backup at either CB or LB :)
I think we need one LB, and we then have 7 senior players for the 8 positions, and Josh Wilson-Esbrand for emergency backup at LB, and Phillips at CB (again he's played there for a season early in his career, and has stepped in regularly since). That's more than enough.
If we get Cucurella (or someone of a similar level), then we'd have 7 players who will expect to play regularly. If you divide the minutes of 60 games by 7 players, then you have around 3000 minutes, even without JWE and Phillips. Last season Cancelo played 4600 mins, Laporte 3750, and Dias 3300 from fewer games. Cancelo needs to play less, but overall it means that we've easily got enough players to cover those games.
So, I'm fine with us buying one LB, and having 7 senior pros + JWE, as we have flexibility throughout the squad.