QGIS buffer polygon with different widths on each side

I create maps for wildfire risk assessments and am constantly asked to plot "defendable space" buffer zones around building envelopes that are different distances on different sides of the buildings. (See image)

I have been doing this in QGIS by creating a buffer for each distance required and then manually drawing one that matches as close as I can.

This is obviously less than ideal. Is there a way I can create these buffers with QGIS? I also have access to ArcGIS and MapInfo.