I'm getting aprox 4 g's worth of shots from one charge; do we really need an extra bat? How about a new base plate that has a grip, holds an extra SD card or two and a bayonet mount to hold an additional lens like we had for out film M's?
I'd buy one in a minute, as this would be very useful- 12mm on the camera and 21mm ZM on the plate or 21mm ZM on the camera and 35 lux on the plate. I can dream can't I? : )