Re: the baseball-- I interpreted more in terms of Kira's arc. The baseball was used to symbolize Sisko determination to return. However, it was also used to symbolize the desire to command and control the station, as in how Dukat plays with it in Sacrifice of Angels. In WYLB, Kira isn't content to leave the baseball. She picks it up and plays with it, as if to say she stepped into Sisko's (political) role. It's her ball (and her station).