By using viewBox and a container element (of whatever size) I think you can achieve the effect you’re looking for: http://jsfiddle.net/davegaeddert/WpeH4/
<div id="svg-container" style="width:100%;height:100%;">
<svg width="100%" height="100%" viewBox="0 0 100 100" preserveAspectRatio="none" style="background-color: whitesmoke">
<rect x='40%' y='40%' width="25%" height="25%" />
<polygon points="0,0 0,100 30,20 30,0" />
<polygon points="30,0 30,20 60,0 60,0" />
<polygon points="60,0 60,0 90,30 90,0" />
</svg>
</div>
If you give the viewBox a size of 0 0 100 100 then the points can be written like percentages and the shape will scale with the svg.