I'd like to see native virtual monitor display splitting. Large, high-resolution displays often beg to be subdivided into smaller displays but treated as if there were separate monitors. I feel like a lot of screen space is wasted with wide displays, especially with applications and web sites that don't take advantage of it well.
I've tried several utilities that do this, but none were all that usable or useful. Display Fusion will do it well, but only even divisions. Uneven splits are coming but it's been several months since they said they would add it. And I'm not sure it will allow for things like 3 way splits (ie, one portrait with two landscape next to it).
I'd also like to see the opposite, display combining, treating a subset of monitors as a single monitor. Even though the bezel is an irritant, there are times where it would be nice to treat more than one monitor as a single display but not be forced to accept it across all displays.
Being able to scale virtual displays would be nice, too, the way you can with RDP. It'd be nice to take a keep-track logging or status window that really needs a big window to be used but could be scaled into a smaller window to be just kept an eye on, even if it wasn't totally usable.