The National Defense Act of 1916 did not replace the Militia Act of 1903.
The 1916 law dealt with funding of the National Guard, which was officially created by the 1903 law, and creation of the Reserve Officers Training Corps.
None of the subsequent legislation ever redefined or disbanded the unorganized militia recognized in the 1903 law. They all related to funding or organization.
You’re welcome to try all the grammatical gyrations you wish, but the fact remains that the militia clause is either a prefatory clause or a dependent clause, neither of which limit the operative clause, which is the right of the people to keep and bear arms.
It doesn’t really matter, anyway. The Second Amendment doesn’t confer a right; it prohibits the government from infringing on a right that existed before, and independently of, the Constitution. Nowhere does it say that the maintenance of a militia is the only reason for the people to keep and bear arms.
As I have said before, the Second Amendment is like the First Amendment: it is a prohibition on the federal government and later on the states.
Of course, you could change or repeal the Second Amendment. All you have to do is to get three-quarters of the states to ratify it. In fairness, it would take just 13 states refusing to ratify to kill a new amendment, but that’s how it goes. Note that 44 states have language similar to the Second Amendment in their own constitutions and those would have to be changed, too.
I should point out to you that South Dakota just became the 14th state to adopt Constitutional Carry. This means that the citizens of the state no longer need to have a state-issued permit to carry a concealed handgun. Oklahoma is on track to become the 15th state, since the Oklahoma house overwhelmingly approved the legislation, the state senate is also likely to approve it and the new governor has already said he will sign it.
In addition to the 14 Constitutional Carry states, 17 other states allow open carry of a handgun without a permit.
And then there’s the decision of the Federal Appeals Court for the Ninth Judicial District’s decision in Young v. Hawaii. The court held that Hawaii’s decision to not issue or reissue carry permits is unconstitutional because the Second Amendment guarantees the right to bear arms. If it is upheld by the Supreme Court, the “may issue” policies of a number of states (California, New York, etc.) may be ruled unconstitutional. It’s possible that the court could say that it is unconstitutional to prohibit the carrying of firearm without a permit, so long as they aren’t concealed. It’s perfectly fine to restrict concealed carry as long as there is a way for citizens to legally bear arms without the need for official permission.
The Supreme Court hasn’t accepted a Second Amendment case since McDonald v. Chicago in 2010. With the additions of Neil Gorsuch and Brett Kavanaugh, it will be a lot easier to get the votes required to grant certiorari for new cases, like the New York City case that will be argued this fall.