I have done post-incident analysis for another dangerous sport, cave-diving. We had to examine the some 27 deaths, some involving people we knew. If we learned anything, it is that you will find cases for anything know matter how much you believe it isn't possible. Yes, riders have had serious injuries wearing suits that were not all-cow but there are also a very large number of road racers going down on a regular basis, including some who apparently aren't very good or lucky, that have gone down over 20 times a year wearing suits with multiple fabrics. Injuries also occur with all-cow suits. If you look at many of the amateur and pro series require you will find it is 2 piece suits that almost all of them don't allow. All allow perforated leather in specific zones. Properly designed stretch zones also do a very good job of minimizing loose 'bunchy' leather that is well know to do serious damage to the skin during incidents.
I don't feel there is legitimate justification in declaring anything non all-cow unsafe especially in the 150 mph and below range. It is like saying we know better than all other series despite most of them having much more incident experience. If a ruling should come out on this, I hope that it is similar to the 4 wheel rules where more gear is required over a certain speed be it 140 or 150. We should also make an effort to make post-incident analysis public, after a cooling off period, so we can all feel comfortable with the rules.
One area where our sport does differ is with high speeds exceding 200. Only drag racing has that in common with us and I am not sure that they have it down to an a science. We are also unique in running on salt though road racers have some pretty rough gravel pits to deal with. I don't want riders wearing potentially inferior non all-cow suits, but we need to be sure that we don't end up with riders wearing inferior $350 all-cow drag suits due to a rash ruling if they would be safer in the $1000 road racing suit they already own.