They love Klay Thompson, and they'll have more than adequate backups in Jack and Rush next year
Yeah, they really do love the guy, and for good reason. He's 6'7 and has a very high release, demanding a lot of attention. I think that's why Golden State would benefit putting him as Pierce's main back up 3 (as well as back up 2 or starting 2) - he's really flexible in that regard.
You could go big - Curry, Klay, and Pierce
You could go small - Curry, Bradley, Klay, Pierce (Pierce is really strong - could work against undersized 4s)
You could go clutch - Jack, Curry, Pierce
You could go defense - Bradley, Bogut

, Rush
There are so many combinations. Golden State has been playing small ball a lot lately anyway. Your basically taking an already deep wing rotation and making it way more deep and versatile. Replacing a 3 and D guy for someone who's really good at defense and another who's really good at scoring makes for something Mark Jackson would love to figure out how to utilize.
The fact that you don't have to rely on Bradley to handle the ball much means that he can go full throttle on defense for 20-25 minutes a game.
Also, from a financial standpoint, they shed Jefferson and Biedrins' horrible contracts and get an expiring one a la Pierce. I don't know their cap room situation, but taking out potentially 35 million together is pretty good.
Their front court gets better too, imo. All of them minus Bogut are offensive talents that all provide something. Landry pounds it inside while Bass spreads the floor. Lee both spreads the floor and pounds it. Bogut is the defensive backbone. They could use the 16th pick to get maybe Gobert, Plumlee, Noqueira, or trade down and pick up Steven Adams, Dieng, or Withey.