Josh Hamilton is another option, but he'd cost a ton, would give the Phillies three straight lefties in the middle of the order and there's no guarantee he could even play center a year from now. He also has a lengthy history of injuries and substance abuse.
It really would depend on the creativity of the contract -- Phillies fans could talk themselves into a lefty-heavy middle of the order if it were to happen.
Read more about this from Corey Seidman at CSN Philly: Who stays? Who goes? Phillies center fielders.