b)are they gaining an advantage..answer: by bringing in their kicking team when not allowed..
Yes, it's not allowed by rule, but are they gaining a real advantage in doing so for the last second field goal attempt when everybody and their grandmothers know they're going to kick a last second field goal attempt? Football tends to be an overly conservative game as far as strategy goes, but intentionally running a fake field goal play as time expires is a bold strategy, Cotton, let's see if it pays off for them.
I like the Louisiana rule that states you have to kick the ball in that scenario, just to prevent any shenanigans, and then that completely eliminates any potential thought of advantage gained because your right tackle is number 87 and not 78.
I'm curious how it'll work with botched snaps or other breakdowns in the play -- is it a foul for illegal numbering if there's a high snap that sails over the holder's head? What if he gets the bad snap, but the delay allowed a defender to tackle the holder prior to the kick? The defense would likely decline the penalty in those scenarios anyway, but it seems more "salt in the wound" rather than illegal advantage needing penalized.
The number requirements do not exist on a scrimmage kick...correct? How about on a PAT where the go for two? Would you ever call 'Bad Numbers' on an attempted kick where the holder didn't secure the ball and they got into the endzone scoring 2 points?
"Do not exist" is overstating it, but I get what you're going at. You can legally have no players numbered 50-79 in a scrimmage kick formation on 4th down or a try down. You can legally have 4 of the normal 5, with the snapper as the exception, on 1st-3rd downs.
If they're not in a scrimmage kick formation, you need 5 players numbered 50-79 on the line, period, for any down. What happens after the ball is snapped is not relevant to the formation/numbering at the snap.