I would never do such a trade.
First, we don't even know how Exum will player after the knee injured that he suffered in the summer. Second, Isaiah's scoring ability is the special something that we have lacked for a long time, which I don't think Exum or a player picked in the top 12 can do just as well (maybe Buddy Hield?). Third, IT averaged 26.5 points, 4.8 assists, 3.7 boards and one steal; shooting 47.8% from field and 42.6% from three in the month of March, which is why I personally would like something better in return for a player putting up those numbers.