Most of us see the 2A and RKBA as absolutes, a right explicitly identified by the Founders to allow us to own, carry and use anything. But what if (hypothetically), the Founders had a different interpretation, and could clearly tell us so?
Would your personal opinion change?
There is an inversion in your hypothetical that ignores how natural rights theory was developed and the precise meaning of the Constitution and its enumerated powers.
To begin with, no government grants rights--the rights are inherent to individuals and the only just government protects those rights. They are not collective rights. Now, the right to bear arms comes to us from the struggles in Great Britain over the nature of a king's rule over England. The Glorious Revolution ensured that kings could not use mercenary armies to thwart the will of the people expressed through Parliament by the English Bill of Rights in 1689. In other words, they forced the new King and Queen of England selected by Parliament to express their agreement that these were the ancient rights of the English and to protect them, including the individual's right to keep and bear arms.
Those settling in the American colonies at the time were favorable to Whig political theory as it agreed with what they found and believed to be true. Then, they set about creating their own charters, etc. that explicated directly the social contract between the government and the governed. Included in these contracts were certain basic rights. When King George III attempted to destroy these rights of colonists, including the right to bear arms--(after all the whole point of the British expedition to Concord and Lexington was to seize arms owned by the individual minute men.) Note, no one or government made these minutemen show up, take up arms, and risk their lives. They did so as a collective to protect their rights from the English but would not tolerate one among them who was chief to be allowed to disarm others.
After petitions were ignored by the King, then came bloodshed and revolution due to the King's unwillingness to recognize that colonists should have all of the rights enjoyed by Englishmen in Great Britain.
The Revolutionary War cemented the ideas that governments must be limited in scope and protect the rights of citizens. Virginia adopted a Bill of Rights before they declared independence as they felt it was so important. Other states did to.
Then came the fight between the Federalists and Anti-Federalists over a Bill of Rights. The Federalists felt that none was needed because the Government lacked the enumerated powers to violate freedom of speech, seize firearms from individuals, demand all worship a national church, and so forth. If you look at the Constitution itself, there is no power granted to the federal government to take citizen firearms--period. Instead, it gave Congress the power to create an army and navy and to allow the Commander in Chief to take charge of states' militias in the event of war or rebellion.
Using the necessary and proper clause, Congress can then attempt to make the state militias more effective through providing regulations to states that indicate to some degree how those militias are to be made militarily useful to the U.S. national defense to resist any invasion or rebellion. Remember the national army was extremely small during the Articles, and Congress debated whether to even create a national military. In any event, due to the size and poverty of the U.S., the brunt of protecting the U.S. from Indians, foreign troublemakers from French, to Spanish, to English, and from each other such as the Whiskey Rebellion, meant that militias were the new minutemen that would forestall such things until the regular army could come to their aid. The onus was on the states and the individual companies of average Joe citizens to protect their homes from rebellion and invasion. Without individuals owning their own arms, mustering on their own time, training and providing such materials from their own purse, there would have been few if any militia as states as well as the national government lacked the ability to finance them. Some individuals even had ships with cannons and others, along with communities, banded together to buy such things and provide for poorer individuals the supplies needed. These were truly organic, not governmental, societal organizations that viewed their service to government as service to their friends and community rather than the larger world.
The fear of the Anti-Federalists that the new federal government would be a tyranny led them to oppose ratification unless the new Constitution had a Bill of Rights. The Federalists generally felt that a Bill of Rights would be dangerous as it would lead tyrants to figure out ways around them and no Bill of Rights could encompass all possible existing rights at the time. The Anti-Federalists persisted and darn near derailed the Constitution in Mass at the Convention there. Thus, the Federalists caved and proposed that the new government should adopt new constitutional amendments aka Bill of Rights. Subsequent ratifying states, especially the important ones, like Virginia agreed. Thus, the Bill of Rights was proposed by the 1st Congress and ratified by the required number of states on Dec. 15, 1791.
If you look for what the Framers thought about it, you could quickly look at the state constitutions of the time which supported an individual right to firearms (if they had a bill of rights which some states did not). If you want the compilation, you may want to read, THE COMPLETE BILL OF RIGHTS: The Drafts, Debates, Sources, & Origins, Ed. Neil H. Cogan (Oxford Univ. Press) 169-205. 9 states mentioned the individual right to bear arms in their state ratifying conventions, ten had provisions for the right to bear arms, (some by implication of militia service) in their constitutions. Much of the discussion in Congress revolved around the idea that standing armies are dangerous and a national standing army of such as size to defend the U.S. would be A) an agent of oppression B) not affordable. Thus, the discussion then devolve over what power the National government should have to make sure the militia were fit for national service--that is training and supplies. States would be responsible for the rest of the organization and the federal executive could only command the militias upon being mustered into federal service by Congress. Some of the discussion was over individuals right to use arms for self defense as well as hunting, etc. There was no consideration that government had the power to deny citizens the right to keep and bear arms. Most would agree with Blackstone which then implies some means of self protection, ..".there is a natural law of the right of resistance and self preservation, when the sanctions of society and laws are found to be insufficient to restrain the violence of repression." Commentaries on the Laws of England.
In America at the time, there were few police, a very small army, and very real threats of invasions, rebellions, and other disorders. Thus, most households, perhaps outside of the few major cities, had firearms available. The National Government in its militia acts during the 1790's, relied on this self arming by citizens to create an effective militia. That did not imply that the keeping and bearing of firearms depending on militia service, simply that if a person was in the state militia that Congress could mandate certain standards of supply and training for these individuals. However, to carry this out, you must have people with individual firearms on hand, not those kept in a central armory for issue. Community powder storage facilities were largely for public safety due to black powder dangers in large amounts.
Not one member of Congress, not one reported instance of debates of the Amendments or the Constitution itself, etc. had an individual arguing that Congress had the power granted to them by the Constitution to disarm the people of the U.S.
