To try and answer the OP's convoluted question, yes, a blanket ban would be unconstitutional imo.
For Al Norris, are you assuming we'll get strict scrutiny? I hope we do but believe we won't. Doesn't it seem to you as though we'll end up with some intermediate form?
For Brian Pfleuger, Gura thinks the common use test is the primary contribution (outside of the ruling itself) from the
Heller case, and further, that "in common use" actually means, "in common use, or
would be in common use".
He was addressing a question along exactly the lines of your "concern", where, if a weapon is banned and vanished from the earth, wouldn't it then automatically fail the common use test? He said no, and then explained it with the "would be" verbiage, adding that "would be" is how a newly-invented weapon could also pass the common use test.
I'll try to find the video, it's about 90 mins, but well worth it.
Here it is:
http://www.youtube.com/watch?v=pNN7_TOvaUo