For those Canon camera battery grips that use two separate batteries, I sure with some 3rd party companies would produce supplementary trays into which the batteries firmly click-locked. I still find loading new batteries in the field entirely too fiddly with the tray style. I'd love to have a spare tray already loaded with batteries locked in so that I could just do a quick slip-out/slip-in.
Maybe they could even partner that with a battery charger that accepted the loaded tray and charged both batteries while still locked into the tray.
