I think Coutinho is fine as part of an attacking midfield three, plenty of teams have a player that high up the pitch who doesn't necessarily contribute a lot of goals. His ability to find space and then beat a man so deftly allow us to very quickly switch from defending to attacking, what we need is quality players around Coutinho who complement what he offers. Firmino looks like a good fit in that #10 role, and Benteke and Sturridge offer the quality up top, we just need someone on the right who has pace, goals and movement to his game, which admittedly will probably be quite a pricey purchase.
Coutinho right now just looks like a player who needs a little weight taking off his shoulders, something Firmino and Benteke can offer when they're both sharp.