Caicedo would come in as cover for Casemiro and as a defensive 8 option too, so he would basically replace McTominay and Fred at once. I'm also convinced Casemiro and Caicedo would make a menacing combination as the deepest 2 midfielders against tough opposition as they're both very all rounded, with 2 playmakers, one as a 10 and one on the wing, in front of them.
Seeing how many points we drop and how much worse off we are without Casemiro, I would put a quality second DM that can also play as an 8 as a higher priority to someone like Macallister. Currently we have Eriksen, Fred, Bruno, McTominay, Mainoo, Mejbri and Iqbal that can play as an 8, Bruno, Eriksen, Amad and maybe Sancho that can play as a 10 but only Casemiro that can reliably play as a 6. I'd go as far as saying we don't really stand a chance winning the league without a quality back up DM, as Casemiro loves a card and is only getting older.