There isn't a lot of stopping power in the rear brake on any bike. Adjusting the lever isn't going to get you more power or mush more feel. And if you think the rear brakes on the Breva are bad, you should try riding an SV650... that rear brake doesn't work AT ALL until you stomp on it and then the rear wheel just locks up unpredictably. Riding my bike when I bought it was like finding jesus in the way of what good brakes really are. The Brembos on the Breva are positively amazing in comparison because you have the ability to modulate. I don't think rotating it will give you more stopping power or more modulation. From looking at my bike, I don't think what you're describing is possible, not without changing the mechanism that actuates the brake lights.
Try flushing your brakes before you start playing with the lever, I've found that to do wonders all by itself.