I would vote for #1 or #2, simply because as Monte noted, I have never shot a MR match where a single shooter from this class was even present. I recognize that the folks that DO shoot in this classification might not be too happy about that, however. In contrast, I have seen quite a few people using ARs in F-TR, which were set up for that purpose, primarily with longer than normal barrels. In many cases, they did pretty well. The only issue I would envision might become an issue with #3 is if it became mandatory to include the classification with awards at every F-Class match held. I guess you could get around that by stipulating there must be a minimum number of shooters in a given classification to warrant an award, but it is not always possible to know how many shooters will sign up well in advance when the awards may need to be ordered.
I'm not trying to step on anyone's toes or intentionally exclude shooters that participate and enjoy this class, but it hasn't seemed to have caught on universally like I expect the NRA folks were thinking it might. Unless the participation level warrants inclusion, it just seems like potentially more headache to insist it become a standard sub-classification within F-Class.