This odd question comes from believing that such an analysis is plausible in a GIS system.
Only, I don't how to accomplish the various discrete steps implied from the Title, nor where to get a topo map that already has the iso-elevation contour lines developed in some GIS format, nor how to color in areas which face SW-to-SE, nor how to decipher the physical slope from the proximity of iso-elevation lines.
All these things, sensible to the engineer in me, but wondering what set of stackexchange questions (or other resources) might even begin to answer my question....
...in my ideal world, I scan in a USGS Topo map for the region of my interest, and out the other end of my QGIS black-box procedure comes a map with polygons lit up as my areas of interest.
What tools and techniques....? Learning resources....?
[and, if anyone wants to suggest 4 other appropriate tags, let me know....]