As a variant on the same theme, what about having the same model open in multiple windows? Possibly via having multiple instances of the MoI UI communicating with the same backend model (in the MVC sense). I assume that this would be a whole lot of work, unless you've specifically designed for it, but it'd be wonderful, from my perspective, especially if it was possible to run the different windows with different UIs -- multiple monitor support, but in a nice, general, flexible way, and the ability to (even on a single monitor) do things like have two independent 3D views. A low priority feature to be certain, but it'd be wonderful to have.