For me, I have neither a trailer nor a vehicle capable of pulling one, so if such a rule came into place it would become too costly for me to compete in a non-trailered OD class that now would allow others in the class to trailer their cars. So I might as well quite now. Since there is a trailered class, then trailer and be judged that way. If there are ‘cheaters’ then fix the rules to validate cars in a non-trailered class that they in fact drove it to the show.
A trailering rule ‘exception’ would mean that members/owners like me who don’t already have trailers or appropriate tow vehicles and can’t afford them, now have to complete against not only the cheaters but this new group that is in the exception class and can trailer but register in a non-trailered class.
You either compete in a trailered class or non-trailered class, adding a hybrid class (some trailer some don’t) that has to compete with each other only adds more confusion and division in the Class.
If one only goes to a National once every few years and isn't interested in a medallion and goes primarily to socialize with friends and owns a trailer and tow vehicle, then trailer it and register as display only and have fun.