AB, what am I missing in your interpretation.
Let's say we go to the no more than 4 in the backfield rule, so as not to penalize a team for playing with 10. Unless they missing player on the line is an eligible receiver, there would still be a foul. THAT foul is what I'm trying to eliminate. Why should we care if the missing player is an end (eligible number) or an interior lineman. There is still no advantage gained by the offense by playing with ten.
So if we change to no more than 4 in the backfield and don't change the 5 numbered between 50-79, we've really accomplished nothing in terms of not penalizing a short handed team. However, if we go so far as to eliminate the 50-79 numbering altogether, we are back to the A-11, and no
one rational person wants to go there.
I think wvoref may be on to the answer. We don't require at least 5 players numbered 50-79, we require no more than 6 players with eligible numbers. That way, if a team has 4 in the backfield, 6 on the line, and the missing player is an interior lineman, there is still no foul. If a team has 11 players, and wants to use an 8 man line and cover up an eligible number, that's OK too, which would have been a problem with my suggestion.
So, the new 7-2-5 should read:
ART. 5 . . . Player formation and numbering requirements include:
a. At the snap, at no more than four A players shall be off their line of scrimmage.
b. At the snap, at no more than 6 A players may be numbered 1-49 or 80-99.