OK.
So you're saying that there's a 2nd Amendment right to high-yield strategic nuclear weapons?
I don't think those can be reasonably used in self-defense in a manner that doesn't violate the right of others to the quiet enjoyment of their liberty and property...
In the colonies, your average Joe was expected to be ready to serve, bringing his own gun and ammo ( although provision was made in many places to supply arms who did not have those of their own ) at a moment's notice.
In this manner, an armed force could be called up in a moment's notice ( aka Minutemen ). In the main, this would be infantry.
If you look to the writings of David Kopel, the Founding Fathers may have been impressed by experience, and also the cantons of Switzerland, when the 2nd Amendment was drafted.
If you read further into the Federalist and Anti-Federalist, the common theme is that an armed populace would be a strong deterrent to ursupation.
You could secret one near the keel of your "innocent fishing boat", and set it off in the middle, or even near the edge, of an enemy invasion fleet, some miles out to sea. Kinda far fetched, but so is getting your hands on one in the first place.
Besides, neither utility nor even practicality affect the right. The founders probably didn't envision nukes, but they are still "arms" and thus keeping and bearing them is protected. If you don't want people possessing them, and you think it's a problem, it behooves you to get the second amendment amended with an exception for nukes, or WMDs, but be sure you define what you mean, or the gun grabbers will define anything other than a .22 single shot break action as a WMD. Of course those who would harm others with nukes won't turn theirs in after the amendment is passed and laws banning possesion of them are passed. Same problem as with regular gun laws.