Change of pixel dimension
When you want to change from resolution 800×480 to 1024×600, there is a slight difference in pixel dimension to retain circle shaped objects. So idea is that you are able to change pixel dimension and convert some files, instead of drawing new ones. For example-you have a circled object in some .ai file, where you have square pixels. If AI would allow to change pixel shape to rectangular, like 0,14 mm height and 0,15 mm width, or 0,148 mm,..., then it would fasten up things of making same graphic for different screen resolution with tool of pixel dimensions, instead of drawing whole new screen.
Not sure I get the idea.
Are you talking about Pixel Aspect Ratio, like in photoshop, or something more like liquid layouts in InDesign? Can you show some examples of before and after, please?