I've never been much into the 'nuclear' setting, seems a bit too random to me. So, here's my suggestion: Rather than the current system of the territories that are on the cards being turned in getting nuked, allow a target territory to be selected. The selected territory has its armies reduced in the following way:
25% Reduction for Red Set
50% Reduction for Green Set
75% Reduction for Blue Set
100% Reduction for Rainbow Set
The territories on the cards turned in would then each receive a -2 'bonus', the opposite of what they get in other game settings.