I am not sure if Kawhi is injury prone or just plain broken down but he is not going to hold up at this point.  NO WAY I trade Brown for him in any way, shape, or form.  Not even Kawhi and 4 picks.  He is headed down a John Wall career path.  I don't think Kawhi is going to be able to stay on the court and he has 2 years after this at top dollar contract.
Now if this is predicated on Brown giving the Celtics an ultimatum, trade me or I leave, maybe you consider Kawhi and 4 picks.  But I don't believe that ultimatum will be delivered.