I think this is certainly something a lot of Androidteers would like to see, but unlikely on the Incredible. Although, i am aware of htc making phones with slide out querty's that do have such a feature.
I could see it being a pain with lag, but I'd support it.
Also I wonder how it works with your current set up of home screen (apps/widget) ? I never figured out how G1, MyTouch Slide, Droid, Droid 2, Moment, Intercept do it.