A look at the squad from the point of view of squad quotas:
KEY
Club-trained and under 21 (unlimited)
Club-trained and over 21 (4 squad places reserved)
FA-trained (minimum 4 required)
Non-FA-trained players (17 allowed)
Goalkeeper: Karius, Mignolet | Ward, Bogdan, Fulton
Centreback: Lovren, Sakho, Matip, Gomez | Wisdom, Ilori, Jones, Williams
Rightback: Clyne, Flanagan | Randall
Leftback: Moreno, Smith
Midfield: Milner, Henderson, Lucas, Can, Allen, Grujic | Brannagan, Chirivella, Stewart
Attacking midfield: Milner, Coutinho, Firmino, Mane, Lallana | Ibe, Kent, Ojo, Markovic, Alberto
Striker: Sturridge, Origi, Benteke, Ings | Balotelli
Not counting the players on the right side, the first team squad is currently made up of 25 players, 10 of which are trained by other FA-clubs (no problems there), but only 2 (Flanagan and Smith) are club-trained.
This tells me that, at the very least, two non-club-trained players need to be moved on for the squad to abide by the squad quotas. For example, Allen and Benteke leaving would mean that the squad was within the rules again. However, further trimming to the squad would have to be made in order to fit in Markovic/Luis Alberto/any new signings.
In other words, if Klopp wants to sign Dahoud and Chilwell for example, that would mean finding 2 spaces for them - over and above the 2 that Allen and Benteke are likely to vacate. The most logical fall-guys in my mind (beyond Allen and Benteke, and in no particular order) would be Lucas, Mignolet (i.e. with Ward being backup to Karius), and/or loaning Grujic out for the season (unlikely).
Needless to say too, it's tough to see Markovic, Alberto, Stewart, and/or Ilori being able to force their way into the squad, particularly as Brannagan, Ojo, Kent, Chirivella, and Williams are all club-trained and under 21 and as such capable of providing squad depth without taking up a squad place.