I think that if NADAC made a change in dogwalk specs NADAC would basically disappear in the Illinois area. We have very few trials as it is and those trials are getting smaller each time I go to one because there are so many venues to compete in locally. We already don't get a lot of crossover from other venues and if the dog walk becomes different it would cut down our crossover people even more. As it is, NADAC is "slatless" which I LOVE, and competitors from other venues are OK with, but if the height is changed, I can see more of an issue.
I also thing the striding of a dog on an 8' vs a 12' dog walk is different. And while it would be closer to the ground, I could also see a LOT more dogs (especially the bigger dogs) launching from higher on the ramp simply because their momentum would carry them. An yes, you can train a stop at the bottom of the ramp but I train a bull mastiff who I wouldn't want her to stop at the bottom of the ramp simply because of her weight and stress on her shoulders. And while a fall from 4' is higher than 3', I have found that most injuries are not worse from a height, but in how the dog actually lands from the fall. And if you simply lower the height of the DW and leave it at 12', it would just encourage speed because the ramp is not as high and the angles are lower. I think this could potentially cause more falls. I do agree that the wind can be an issue at outdoor shows and when I run my little dog (11 lbs) he has had issues with the wind but this would happen regardless of the height of the dogwalk.
IMHO, dog agility CAN be a dangerous sport. Even with our best intentions, our partners can get hurt. But they can also get hurt chasing a ball in the backyard. It is up to the handler to make the dog as safe as possible in any game that we play with them. There are always going to be distractions in the ring. I had my dog jump from the dogwalk because the judge standing right next to it had on a BIG, brightly-colored, flower-bedecked floppy hat that was blowing in the wind. So while things like screaming, banging, camera shutters are all distractions, they can be trained for by doing things like that in class or even at home. When I train my dogs in the back yard, I often have kids in the neighborhood running around in the yard making noise. I have had someone bouncing a basketball on my deck because of of the venues we compete in often has basketball games going on the other side of the aisle. I have people blow air horns because another venue has soccer games going on and electronic timers are used. I do this all while my dogs are on any piece of equipment because a dog can "crash" a jump/hoop, hit a tunnel bag (or a piece of contact equipment the tunnel goes under), or hit the weave poles at a bad angle at these distractions as well. So while I can't train for EVERY distraction out there because there is always something "wierd' that comes up, I feel my dogs are well-prepared on any equipment with MOST distractions out there.