I think the problem here is an inherent one in a written constitution which, like written scripture, ends up being seen as immutable. It is a fact that the reason why the firearms clause is in the constitution is now obsolete becasue:

a) America has a standing army not a citizen's militia which is perfectly capable of defending its own shores and can recruit as needed.
b) I am not aware of the Monarch of the United Kingdom and the Commonwealth having any current plans to reinvade her lost colonies in the Americas. If she does let me know of any such plans, I would be sure to let you know

However, precedent is the lifeblood of the law and I think there has been a mass of precedent supporting the interpretation of that written law to be any citizen may bear arms regardless of the circumstances.

Maybe you should look to the model in Switzerland where there is no standing army (apart from the Swiss Guard who don't count as they are in the Vatican) and every male between a certain age range is expected to bear arms and train as a soldier in case of invasion but generally keep their guns in the house until needed during war.

The trouble with the right to bear arms is that criminals can also bear arms. The trouble with gun regulation is that criminals are rarely known for their respect for the law and so ignore it. This leads to an arms race between police/honest citizens and the criminals where the criminals get bigger guns so the police have to get bigger guns and so the criminals get bigger guns and ad infinitum.

This is a tricky loop to get out of as once you have allowed guns you can rarely manage to ban them again - especially when so many consider it part of their constitutional rights. Once Pandora's box is opened it cannot be closed.

An interesting piece of trivia. For many centuries, nobles and gentlemen of England were not only permitted to bear arms but were actually required to do so. A gentleman of the 17th century could not be seen without a blade in public and there were many fashions around that requirement (hence all the various decorative rapiers on display in many museums). It was (I think) Robert Peel (home secretary during part of the Victorian period, founder of the metropolitan police and source of the name Bobbies and Peelers) who brought in legislation to ban weapons. In Leeds Armouries (a museum of weapons and warcraft in Leeds) there was an exhibition on Victorian weapons and there were an awful lot of 'secret weapons' used after the ban was in place - swordsticks originated in this time, there were a lot of small knives and coshes for the lower classes and, the wierdest exhibit, an umbrella gun. A working shotgun hidden inside the shaft of an umbrella. All of these were made because certain criminals needed secret weapons and certain gentlemen bridled at the loss of their right to bear arms.