Grade the trade: Sacramento Kings' point of view
Mitchell's situation in Sacramento is a bit strange. His playing time has fallen off drastically from his rookie season to the point where he's not even playing half the minutes he did in his first season. He's now the ninth player in Mike Brown's rotation, so if they viewed him as an important part of their future at some point, that no longer seems to be the case. Maybe it's time to try something new.
Beauchamp, as it's been said, is still a bit green, but the potential is there, and he has some things going for him to take a bigger role than Mitchell in Sacramento. He's more versatile, being able to play shooting guard or small forward, and he's a better shooter, something pretty important in one of the few teams that shoot more than 40 3-pointers a night. In that way, he could fit better.
He's also shown some good instincts on his off-ball movement, a part of his game that could really grow next to a great passer like Domantas Sabonis. The Kings' offensive system demands players to be in a constant movement, and while Mitchell doesn't have a big impact on that, Beauchamp may have some potential.
Sacramento would also land Cameron Payne, who's had his ups and downs but can add some scoring off the bench and some 3-point shooting. Furthermore, he would become one of the oldest and most playoff-experienced players on the roster thanks to his time in Phoenix, so maybe he can add some value thanks to that.
In short, the Kings wouldn't be getting a lot, but they would just send a player they really don't seem to trust a lot in exchange. It's kind of a 'why not' situation. If they think Mitchell doesn't fit, why not try what Beauchamp can bring? If he ended up not being all that helpful, they wouldn't have lost a big piece.