There's something about water that makes the same metal water battery work. We all know that water is conductive but If I were to use something like a conductive plate instead of water the cells wont work due to it being shorted out. How can something be conductive but yet not short something out like you would expect? I just can't swap out water for a copper plate and expect it to work like water, but yet both the water and the copper plate are conductive.
Also looking at these cells also shows that not all the voltage is coming from the galvanic reaction that we assume with the dissimilar metal cells. Looking at my cells shows that voltage is there even though we use the same metals for both plates, so a fraction of the voltage we get from dissimilar plates is not from the galvanic reaction. I bet you could apply everything I've learn about the same metal water battery and apply it to a dissimilar metal water battery to increase its voltage, such as having one plate barely touching the water. I bet the same rules could apply, like one end of the plate could be more attracted to the other end of the other plates, such as with polarity. Maybe you could combine the two, where you have a dissimilar plated cell combined with several similar plated cells to make a very unique cells.