You know, quite arguing with us here and just write up a proposal to the ATF already. Most of us here don't think it'll pass, but the ATF answer is the only one that counts.
But, like I said, don't be surprised if they pass an idea "on paper" and later rule it a MG after a physical prototype is built. Google "Atkins accelerator" for an example where they did exactly that.
Btw, leave out all that stuff about being a "Fan of the M2" and the mock-up box that holds a Ruger 10/22. That's irrevelant to your central question and clouds the issue.
You want a clear, unambigious answer and the best way to do that is to ask a clear, unambigious question.