I really don't know where do they plan to play him and how much are they willing to pay for him, it looks like exactly the type of transfer that cost them a lot in the past and that they stopped making in the last 2 years.
Barcelona is obviously looking to get rid of him, he isn't even playing with all their injuries and problems because if he plays a few more games they will have to pay another installment of the transfer to Liverpool. Good thing for Arsenal is that they cannot ask for any kind of significant money.
Anyone that watched Coutinho play knew, he wasn't a good footballer. Yes, he scored spectacular goals, but his technical skills and movements were always very poor. Just watch him play next to LaMasia player and the difference is obvious. I don't think he would make the FC Barcelona B team. Yet, someone managed to pay him massive $$$ and sign him to this massive contract. It is clear, he was brought in as an overreaction to Neymar departure.