I think the last few months have shown the club the way. If the club takes a tough stance (which I suspect they will ) when and if the bid arrives this window, they know that Coutinho will not down tools. He'll be pragmatic and think that as he is now not moving until the summer, he might as well knuckle down and play for the world cup place. I don't think there will be any need to threaten or fine him.
LFC has nothing to lose by doing absolutely nothing, not answering any queries or any speculation until a real bid is tabled and then turning it down. And as recent experience have shown, the player price goes up. With certain players, it could be a disruptive influence (like costa, Sanchez?) but with Coutinho he seems the quieter type unlikely to raise up some dressing room mutiny and discord.