I believe that once we begin reviewing the Militia Act, along with historical letters of marque, we're going to find that a graduated registration requirement will not be that unreasonable.
I don't have to remind everyone here that 'well-regulated' does not mean regulated in the current sense. Rather, it means that one is proficient in carrying out whatever militia duties they may have.
That's why it will not be necessary to register machine guns, since, in lieu of current prohibitions, they are simply common arms.
However, I wouldn't have a problem with Bill Gates registering his aircraft carrier, along with other various hi-tech billionaire pilots being checked out on their F-22s to make sure they can adequately support/complement standing air forces.
If the SCOTUS followed the Constitution, I would have no problem with a ruling that every adult citizen must be trained in the use of arms once a month.