Articles: Relative Auto Margin

When I set the margin of an article to auto, I seem to get some predefined margin in pixels. It would be great to have a relative margin setting that increases relatively with the screen size.

OK, I made a mistake here. I noticed that we do not use the margin at all, as we have article styles that do not use a margin and only use padding instead. It would be great to have a variable padding option for this.