At the show I asked the BMW Rep from NJ about the battery capacity being less. He kindly educated me that the decrease in the 12 amps from 19 (I think from current model) should not be viewed as a problem. It is the alternator that is critical to supply power to the system when in use. It quickly replenishes the energy back to the battery upon startup and continue to supply necessary energy to the system. If the alternator is of low capacity, then it fill not able to supply energy to the system, and will utilize the stored energy from the battery, thus depleting it.
He said the new WC has 580 Watt alternator. Current model has 620. The reduction is sufficient due to efficient use of electrical use. I asked him having additional lights and Gerbing gear will it be able to support. The answer is Yes!
He recommended using additional lights based on LED. It will draw very little electricity. You can continue to use your Gerbing gear, although to keep on mind that this gear uses lots of electricity, upon power-off, make sure you turn your Gerbing heat controller off. (I learned this when fueling my gas tank. I forgot to turn off, it depleted my battery. Lucky after few attempts I was able to start my bike's new BMW battery.)
So I was rest assured that 580W is adequate for the bike.
I suppose using less powerful alternator and battery, both will yield less space and less weight, necessary to offset the weight gained due to water cooled.