A touch screen table would solve that problem. In a perfect world we would have desks whose entire surface is a multi-touch screen, not as a replacement but additionally to "regular" monitors to allow exactly these kinds of interfaces.
Not really--you'd still be using large-arm motions on a large surface, holding up your arms so you wouldn't generate false touches. Even palm detection won't help, as you'd still need the large-scope motions to tie things together.
