Although the 2nd ammendment has been abused by those who would like it to mean to opposite of what it clearly states, there is a part of the constitution which needs to be updated first. That is the interstate commerce clause:
To regulate commerce with foreign nations, and among the several states, and with the Indian tribes;
I think this should be changed to allow the federal government to regulate trade with foreign nations and Indian tribes (although the second really doesn't matter). They should also have the power to declare void any law the states enact regulating interstate trade.
They would then have the power to prevent the states from restricting interstate trade, but wouldn't have any additional power to regulate it or anything peripherally touch it. Probably half of the federal government would be made illegal though that change.
The Commerce Clause has been used as a catch-all for every type of regulation. I boggles my mind how the clause can be used to justify everything from gun laws to handicap ramps. Some of what the feds regulate might not be a bad thing, but it really strains constitutionality.
Mike Bloomberg, erstwhile Democrat and mayor of New York, was asked during a Republican rally "Do you support the 2nd Amendment?" He responded, "Which one is that?" Shortly thereafter, his handlers ushered him out of the room.