Does Congress not have the authority to organize you, arm you, govern you, employ you? Do the states not have the authority to appoint officers over you, or train you according to the discipline prescribed by Congress?
Can you not be called forth to enforce law, suppress insurrection, or repel invasion?
You certainly can make some distinctions between “person” and “militiaman”. A 4-year-old child is a person and not a militiaman. The courts would certainly rule against the idea that Congress can organize a Children’s Brigade under the militia clauses. They would rule on constitutional grounds against paraplegics, or the mentally disabled being drafted. But we aren’t talking about these exceptional cases. We are talking about the general case, and the general case is that it is your status as a person that makes you a member of the militia.
Indeed, I think that Congress should establish a requirement that every American be trained on safe handling procedures, as well as on the laws governing the use of force in self defense and defense of others. They have that authority under the Militia clauses; I think they should exercise it.