Hi,
In fact, increasing the resolution of the battlescape area is not *that* hard, but there is also the problem of the resolution of the GUI...
The graphical user interface department is more SupSuper's area of expertise, but as I see it, the user interface components are not really ready for it. All GUI components, like buttons and textfields, are given an absolute, hardcoded position relative to the topleft of your screen. Made for resolution 320x200 only.
If you would increase resolution just like that, you get all of your components somewhere in the topleft half of the screen.
To fix that these components should be positioned a bit more dynamically.
But that also only can work if the positions of buttons,etc are relative to a parent component that has some "alignment" setting.
For example, the battlescape interface has to be aligned in the bottom-center, leaving two gaps to the left and right of it. And the buttons/text/etc on it, should have relative positions from topleft of this interface-area instead of absolute positions from screen topleft.
I bet it's somewhere on SupSuper's unofficial todo-list, but certainly not very high priority
But yeah, it has been asked for before, so I guess openxcom will see this feature one day.