While this isn't directly an issue, it does lead into one. Let's say in 6 months the largest nation is 200k, and the nuke range 80k. Yet a nation can get itself to 50k, buy a MP and nuke those 200k nations, probably costing more money in damages than they have earnt in the entire life of their own nation! And on the other hand, in an alliance war you're going to have 50k nations attacked by a nation four times their size, which would not be fun.
And exactly because of that: Narrow the range and make no exceptions. If you want to attack someone, grow in his range. Easy as that.