To me that question falls into the category of 'don't ask the question if you're not going to like the answer'.
I don't know whether the FRMS will make a 24 hour rule or not. It would seem a little pointless to me given the distances that some people drive to the airport prior to sign on or what they choose to do before work. So unless the FRMS wanted to make rules on renovating your house prior to sign on, or big gym workouts prior to sign on, or how much the young kids slept the night before sign on, etc, it seems silly to be prescriptive in the one area of 'commuting' to work.
So I hope common sense prevails for this one.