Hi PeterW ... are you back from the sunny southland? And doing well, I presume.
I only have my own experiences to rely on. No. 1, if someone wants to cheat, it's pretty difficult to eliminate it. In benchrest, there are fewer variables to deal with than, say, auto racing. Factory class shooting has even fewer variables. A box-stock factory rifle is fairly easy to verify. At our matches we allow free-floating if not already done, and a lighter trigger just because it's darned hard to do much sandbag shooting with a 12-lb. trigger. We have never eliminated anybody for illegal equipment. If a trigger is questionable, it can be checked. Same with a barrel, bedding, adding pillars, etc.
We have had over 20 different Factory shooters at our matches, including myself who started there. Just off the top of my head, a half-dozen of them ended up with BR rigs and participate in our matches. The others still prefer egg shooting to the "formal" stuff. I have never understood the nitpicking over Factory rules. Handloading, of course, is allowed; couldn't care less what you shoot. If you want to use factory loads or Black Hills or Federal Match or whatever, have at it.
When we first started there was a lot of controversy over allowing Coopers, Sakos, 40XB, etc., to shoot. But we soon found that the Savages, Remingtons, etc. were at no disadvantage and for several years our mantra was, "If you want to win in Factory class you'll have to beat a Savage to do it".
I think the sport is missing a lot of opportunities to introduce new shooters to the sport, put more butts on the benches, and create a lot of interest in the sport by allowing a Factory class that isn't necessarily under the same microscopic micromanagement the "big guns" are. There isn't any "spectator value" to BR shooting, watching the grass grow is as exciting as watching somebody stare downrange for minutes on end, pull the trigger, reload, and do it all over again. So just seeing a BR match is not all that much of an incentive to drop $4000 on equipment and see if you like it.