Barkley is garbage in central midfield but we don't need him there, Dembele, Wanyama, Winks and Dier is a great group. In an emergency, Dele or Eriksen would both be much better options than Barkley. If we get him we should give him an attacking role.We don't need a lot of players just some flexible players to cover.
Pereira can play LB, RB, LW, RW, Barkley can play CM, AM. Those two alone would massively change our depth. Then when we get Son, Lamela, Rose etc back we will be quite strong.
2-3 good flexible players should be enough with our first team and a few good youth players to cover as well.