The key issues with selling him are simple. We only sell him if we have a back up striker with excellent quality secured, and we get a decent amount of money to reinvest.
There is absolutely no point in selling him, even with his drama, if we can't bring a decent player in to replace him. They wont be as good as him, but if we get a 20 goal a season player with a goal scoring midfielder, then we might be able to cope.
The problem is that there are only a handful of players that fit that mould, and they are probably happy where they are. So we can't sell unless we can replace, otherwise all the hard work BR has done will likely go down the drain.