The ability to make your save have a size as in maps have a length that tells you this is 100 miles long.
And aply it to creations as in bombs buildings cities...
Uses would correctly sized corrations as in if I put a bomb in a city it would be able to have a correct size and shrink or grow dependeing on the size of the city and the bomb.
Why not just use the grid? (Press G) This wouldn't give you distances, granted, but it would still give you size ratio if you make up the measurements of each square ;D