It's too much power for 1 person, so how's this. Each time an enemy base is captured, your country gain "parts" for it. Once you have captured all bases, but still have not won the war (example would be 2 v 1 a country into oblivion), the nuke is ready to be dropped. The nuke is free, although it is only enabled from the same base 163s are. So if you want to use it, expect a 1 hour+ flight to wherever you're going. Ample time for the 2v1'ed country to form a defense. And if a whole country of 163s can't kill a couple sets of B29s, they deserve to lose.