None of this changes the fact that the Constitution grants the Federal government the power to organize and equip the armed forces, and nuclear weapons are arms of the armed forces. Under the Constitution, the government can build and maintain nukes, just as it built and maintain ships. Comparing a privateer with WMD is curious, but even if we go with it, there was also an organized Navy; the Americans did not JUST operate with letters of marque.
The argument that the government can't build and keep nukes is indefensible. So we're down to the question as to whether individuals can have personal nuclear weapons. So far, you've argued yes.
Or, maybe you saw that and are a believer in the "living document" deal and don't think it needs "fixed".