He’d be a direct placement not squad filler
Let’s be real here, if Lemar came to Liverpool it would be as a direct replacement for Coutinho. Otherwise it would be madness having him in the squad.
The type of money that Monaco want for him would pretty much use up what the club would get from the sale of the Brazilian, so there is no way they could afford to leave Lemar stranded on the bench.
In contrast to that, Arsenal would still have Alex Sanchez in the side and anyway, Lemar wouldn’t be a direct replacement for Sanchez because he doesn’t have the goals in his locker.
The Reds would be looking to get him straight into the side and give him game time, could he get exactly the same treatment in London?