Wile-E-Carl, Supergenius. OK, practical genius. Very good idea. And by the way, welcome home.
The suspention is the most neglected aspect of the 919. Early bikes wallowed thru turns with the set up that came out of the box, so it was taken on face value that the frame was weak, and if you spent any money on upgrading your suspention, you just tossed your money away because the 919 will never be a Gixer killer. However there are a few of us that question everything, and have changed a few components like springs, and rear shock, and have come up with some very worthwile improvements on the way the 919 rides and handles. Dan Kyle told me once that the front isn't all that bad (`04). Damning praise; be that as it may. The back is simply oversprung. I got lucky and bought a used Ohlins sprung for my weight. I got it fairly cheap. That was the best money I've spent on this bike. However, I think if the rear spring was changed, the stock shock would do quite well. I don't even know if the rear spring can be changed out. It would certainly be trial and error but the stock spring could be carefully be ground to lighten it up to match the load it has to carry. I think there's money to be made with that idea if someone had the equipment or know how to get it right. I think it'd be pretty cool if you could send someone your shock, tell them how much you weigh. They'd grind the correct amount off your spring and your bike would ride the way it is supposed to.