All the arguments here started when some people said it can't be called dressage , can't be judged like dressage by dressage judges and can't be done in their dressage arena.
We now, hopefully, agree that lower level dressage IS dressage, that nobody wants to take anything away from upper level dressage riders.
And a warmblood has a chance in WD as long as it can perform the western working gaits jog and lope, not only trot and canter. I wouldn't go as far as saying it would win automatically.
WDAA uses USDF judges. It is judged like a dressage test. Honestly the outcome will be the exact same as a normal dressage class and eventually people with non-traditional dressage breeds will be complaining again how their horses are beat by the elitist snobs on horses bred for dressage, just now it's in different tack. As was suggested in a previous WD thread, it would be far more "WD" like to have a western gaming event, like pole bending or barrels, and then go do your dressage test and the combined score determines placing. Like in eventing.