The right is to KEEP and bear arms. Clearly a tank can be kept. Just like cannons or cannon armed ships could be and were owned by individuals at the time the second amendment was written.
I think Kopel, while being realistic as to what a Court would find, restricts the meaning beyond what was understood by the founders.
It's all about prior restraint. The first amendment does not allow for it, and neither does the second. But both allow for punishing those who misuse the right. To be charged with Conspiracy one must take some action in towards actually carrying out some illegal act. Just talking about it doesn't count.
If the second amendment were enforced in that manner, you could have your tank and ammo for the cannon, but you couldn't fire it in the neighborhood, (endangering others) and you couldn't drive it up on the steps of the Capital and blast away. Or run the tank over your neighbor's cars either.
You did not read Heller where "arms" are not "any arms" just as the First Amendment does not guarantee the right to speak for any reason.
Here is the salient discussion of "limitations":
Although we do not undertake an exhaustive historical analysis today of the full scope of the Second Amendment, nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms.
We also recognize another important limitation on the right to keep and carry arms. Miller said, as we have explained, that the sorts of weapons protected were those “in common use at the time.” 307 U. S., at 179. We think that limitation is fairly supported by the historical tradition of prohibiting the carrying of “dangerous and unusual weapons.”
They consider sawed-off shotguns are "dangerous and unusual weapons".
Your tank and ship arguments are sunk right out of the gate.