In terms of the bag/kneeling roll, I'd concede that to a kneeling roll being used, but I really am unconvinced it would work for the smallest/youngest shooters to the larger/older ones, and that then you're looking at either a bit of kit the BFTA has to ship around (and all the clubs etc), or asking the shooters to get them, in which case it's another bit of kit, and another bit of kit that could grow.
I can't remember if we now are going to have the same amount of kneelers as standers, but even so, if marshalling is to be employed on the kneeling lanes that's 4 people per GP. If we rely on the buddy system we place a lot of emphasis on those buddies, who may be a new shooter partnering a seasoned AA, or a couple of mates together that others may pour scrutiny on.
As I see it the biggest problem is the bag touching the bum, or being shaped like a wedge either by design or by filling. So my thoughts keep going back to the bag.
I think at least if the standing rule needs to be that if electing or shooting in a designated standing lane only two feet can be used to support the body during the shot, and no bags are allowed during the shot. Because if you're not kneeling legally then crouching on a bag is still standing, but not kneeling... and if people are saying "oh but the rules aren't against it" now, then there's room for it in the future.
So I guess this year's autumn FT topic is kneeling