In January we need Parisi or Grimaldo. Parisi more likely since I doubt Grimaldo would want to usurp Benfica's good run in CL to go down to EL. And I like Parisi more
Then depending on what's Danilo's position going forward we need either a RB or a LCB.
I would prefer to keep him in the middle with Bremer and get a modern RB. Too bad they're scarce.
Dalot is good, at least played good this season, but Utd control his destiny and they never sell in January unless player is garbage in their mind.
Dodo from Fiorentina impressed me, but they just got him in the summer and they won't let him leave for a reasonable price.
I don't like Odriozola and I hate Karsdorp. Frimpong will be expensive probably and I'm wary of sudden wonders from Bundesliga. Especially for Allegri's system.
Simakan would be my number one choice, but he's probably too expensive and EPL bound now or in the summer. A few months ago RBL wanted 40m for him, I'd imagine that's gone up as well.
And then you can take a risk/flyer on Emerson Royal or Thierry Correia maybe. Or Ricardo Pereira who's suffered two big injuries in the last couple years.
Maybe for now the best solution would be to move Danilo back to RB and get N'Dicka similar to how we got Zakaria. Pau Torres is always there too.
Sell McKennie for the best offer and get another winger to help out Di Maria, Chiesa and Kostić.
If I could choose my ideal signings in January I'd go with Parisi, Simakan and Zaniolo (ofc

)
Then you can have a good and deep team capable of switching between 3 and 4 atb like in Allegri's first season.