Seems to me that a simple way to codify "blindness" is to specify a maximum ratio of perimeter to surface area of the districts; or conversely, use an algorithm that minimizes the ratio.

A circle is the minimum, but circles don't pack and leave gaps. Squares work but are awkward to fit onto human settlement patterns (maybe squares would've worked in the 19th century when much development was based on 640-acre sections, but those original grids have pretty much disappeared outside of farmland).

Maybe the optimum approach is to start with a hexagonal grid (perfect packing density--no gaps) and make minimal adjustments for population. Reminds me of Jack Chalker's series of books on "The Well World", which was laid out in a hexagonal pattern. Define a preferred shape and construct the algorithm to minimize the perimeter-to-surface-area ratio, and you'd be in business.

Hmmm...just fired up a drawing program and started playing with hexagons. They have another interesting property: Seven hexagons group into a roughly circular shape (though with a jagged perimeter that probably isn't a good ratio). Maybe a variation on this idea is to divide the country in a grid of small hexagons, say about a block in urban terms, and make adjustments by adding or subtracting small hexagons in the larger district group. You could make a rule that no exterior hexagon could have more than three sides exposed, encouraging compact shapes and discouraging snakelike sprawling districts.

More playing: You can construct very long and narrow districts, but they have to be straight as an arrow. If you try to turn a corner, you expose more than three sides. Even more playing: Fascinating, I can't construct non-compact groupings without that final hex exposing four sides. Maybe this algorithm would work?