If I were United and believed my midfield seriously lacks creativity but has enough workhorses to cover for James’ deficiencies, I would seriously consider hiring him. He is probably available for around 30 million.
I have watched him the past two years at Bayern, and can say that he has playmaking qualities which are almost unmatched these days. He rarely loses the ball, his passing is sublime, and he can create chances for his teammates out of nothing, even under pressure and against deep sitting opponents. Many of his passes where just “wow!”.
The real and only downside is his lack of speed, which prevents him from dribbling on the offense and shows especially when he has to defend a fast player on a counter – in both areas he is useless. Often though, he showed a surprising will to defend even if he was not very capable. He is definitely not an Özil type of player who only pretends to defend, James really tries and even plays physical and tackles pretty often. I never thought he had an attitude problem, although many other believed that to be the case, I simply didn't see it.
At Bayern they had a very similar player in Thiago, whom Kovac preferred because he can play the 6,8, and 10. Kovac tried James on the wing when injuries hit the team, but that didn’t really work because of his lack of speed. James is a true 10, maybe a 8, but in no way a winger.
If you provide James with fast quality strikers, like Rashford, his killer passes will improve your offence drastically. But then you also need to combine him with willing workhorses in midfield who will cover his back on the defence side. If you do both, he will shine and boost your team. But, for instance, I’m not sure whether a Pogba would like to cover and run for him…