Assuming he gets called up on September 1, Cecchini could be the future at 3B. He would get that month to see how he could handle big league hitting. As for CF, a FA may be the answer, but I'm not opposed to JBJ and Betts sharing time out there.
Actually, change everything. If Shane's healthy next year, we have him in RF or LF if we trade Cespedes for Giancarlo, JBJ/Betts in CF, Cespedes/Victorino in LF, and Brock at 3B. How does that sound?