Yeah, new maps come with new textures, which means new Bitmaps. Halo has done it since Halo 2. A new weapon was added in Halo 3 DLC, the golf club, so why not in Halo 4? It has happened before in Halo 3, so Halo 4 can do it too. Sure it may have been technically a gravity hammer with a new model, but that's the point, it had a new model, and a new texture set. The limitations brought up earlier really make little sense when I think of this.
Twinreaper, if you can explain this to me, I'd be happy to understand, because I may have gotten this all wrong.