i know this has been done to eath but if i were Billy Beane I'd do the following
Barry Zito and Kiko Calero to arizona for Brandon Webb, carlos quentin, and jose valverde
 Webb is an extreme GB pitcher, good for the A's good IF defense. Quentin is a great prospect with an amazing batting eye. If we could get Conor Jackson I'd do that too. And while Calero has been superb for us, getting a inning eater like webb is great for the bullpen. plus, valverde i think is still a legit reliever, and we should get him while his values down.
I'd then trade Jay Payton to the Mets for an old favorite, Chad Bradford. Hed replace Calero in the bullpen.

the only obstacle is the diamonbacks willingness to trade Webb right now. but they may also be unwilling to trade Quentin. still, if theres a possibilty, go for it. Quentin is the type of prospect who comes along only once in awhile.