The whole point with limiting SoDs is that they are unrealistically strong. Sure, they were prevalent in history (although not to the massive degree as in civ, i.e. not near what 100 units represent), but in modern history, they have largely been failures, which is what any penalties for SoDs would be trying to represent. The only time when these penalties will be a large determining factor would be when you have an inordinate number of units, and the only time when this would realistically happen is in the modern era, in which it has been proven that stacks are not the way to go.