As a tablet, Surface Pro 3 is still pretty heavy. One simple solution would be to split the battery into two: put the second one under the keyboard. Whenever the tablet is connected with the keyboard, it uses the battery under the keyboard, which recharges the battery inside the tablet at the same time. The capacity of the battery under the keyboard can be customized with different options : )

I'm curious how much of the tablet weight can be reduced. Can Microsoft make a bigger yet light Surface with such approach?