Capital idea, that sandstorm!
Although this is probably going against the intentions of the scenario, I'm now wondering how to easily and efficiently model a sandstorm, just for looks. Preferably in some way that'd take an hour, max. Cotton or steel wool is what normally comes to mind for stuff like this (mist, smoke, fire, etc.) but in this case one would want to capture a sense of motion, of fierce blowing winds. I wonder if painted steel wool would be adequate for that.
To be clear, I'm not speaking of covering the entire board in steel wool, but a few sheets of it efficiently placed in the empty spaces would hopefully give a nice enough visual effect. They could of course be moved around if they get in the way.
I have actually been toying with a slightly similar idea, but set in a kind of misty dreamscape instead, played on a board covered with cotton representing mist. I'm not sure how to justify such a scenario from a storytelling perspective, but maybe some sort of an underworld/afterlife kind of deal, mimicking all those ancient myths about heroes travelling to the worlds of the dead and coming back again. Or just have it be a misty island or something, for a less radical plot hook.