Mavs will have to choose between him or Josh Richardson. Or even pick totally new player on SG position. If Mavs keep both, then there is no chance to get another good player next season on forward or power forward position where are the weakest.
I guess Mavs should choose the one who is performing well during this season, and IMO, Hardaway Jr. is the better one and he should stay. If they want to save on the salary cap, they probably trade KP as he is a high-value player and they can get good players in exchange for him.
In my opinion yeah you can but the whe point of trading away multiple first round picks for him isn't to just trade him away which you aren't going to get great value back. There is injury concern for KP and no one will give mays what they gave up for him. Their best bet is to cross fingers and hope kristaps lives up to the hype at some point