"My first choice would be repealing the 1968 GCA, which would really put a kink in state laws that depend on it for definitions and regulatory bases."
You are so correct. Although the import ban of 89 and the 86 machine gun ones need to go badly too.
And retool the 34 NFA a lot too. I'd raise the taxes to $1000 but make it easier otherwise to get things. Perhaps make it a licensed thing like with CCW.
Effectively, it's just like CCW, although they had the honesty to call it a tax back then. (Well only because the tax power was the only way the courts would let them do what the Constitution clearly said they could not do. Times have changed) It comes down to begging the government for a license to exercise your Constitutional right.
However things can be set right by increments. To start, eliminate the tax, or at least reduce it to a fee to cover the costs of issuance. Remove the CLEO sign-off requirement, and make it "shall issue" and base it on the same instant background check as for other arms.