I am with you on this. While Sagna was here (especially during the Arteta days) we occaisionally went to 3 at the back when in possession, with Arteta dropping back inbetween the CB's and the full backs pushing forward.
Crossing was absolutely an ideal skillset to possess and Sagna absolutely had room to improve there. Especially when the forward wide men were Walcott, Podolski, Gervinho etc, all trying to get inside as opposed to staying wide.
Marvellous defender though and I still wish he stayed as a CB.