don't see a reason to do it. You've got map Tools to measure the distance between 2 points

There is a protractor available, but that cannot be rotated (unless I missed something) so you can't measure diagonal lines accurately, so there is value in this request. I sometimes use a real ruler held up to the screen as a workaround.

You can rotate the protractor with shift. But it only measures distance out to 1000 meters at a time. Why not make it easier? Or add the shift-click waypoint from ArmA 3

make a line where you have the 1k mark, measure further, next mark etc... why make it casual?