Well, removing oiption Mingueza from Xavi is worth it tbh
Maybe.
But if Alves is unavailable I'd still prefer a Mingueza-Pique-Araujo-Alba backline over Araujo-Pique-Lenglet-Alba. Of course also depends on the opponent but I think Araujo's athleticism is desperately needed at CB and he's somewhat wasted as a FB although he's done well playing both at RB and LB (very limited sample size though).
Xavi doesn't need to play Oscar if he doesn't trust him but it's dangerous going through 6 months with Alves and Alba as our basically only full backs as neither Dest nor Balde seems to be in Xavi's plans. Unless they'll bring someone who can cover both positions in next 10 days but I doubt. I still think Xavi's priority is Morata and he's willing to give up depth in other positions to get him. Not sure if that's really what we should be doing tbh. Now if we could sell Dest for around 30m I would totally understand that move but loaning Mingueza is another thing imo.
Should also keep in mind that for EL we can only register three new players with two of those spots already reserved for Alves and Ferran. At least one of Jutgla and Abde will already stay out (don't think they can be registered for a "B team" list either as they're both only at the club for 6 months and IIRC players should be at the club for at least 2 seasons during their age 15-21 to be eligible for that list). Not that I expect us to go far in Europe and our focus should be on the league but just another thing to consider when doing January transfers.
Also, one reason why I think they want to send Oscar on loan is to free some wages so we can register Nico as a first team player (and then potentially also for Gavi's and Araujo's renewals; although I'd expect a full effect of those - wage increases - would only be starting from next season). Don't know if it's possible doing that without another player leaving and our options are limited. After his injury Umtiti will 100% stay, LDJ also looks more likely to stay than go at this point and I'm sure Dembele will also stay although the club will try to sell him. We'll see what will happen with Dest but reports are he doesn't want to leave either. So Oscar might be the only expendable first team player to lower our cap.