In my opinion Regionals and Nationals are for everybody and anybody that can qualify and it is their option if they want to go. If you want to make it more appealing to some of the top skiers, fine, but there are a lot of average Joe's and new skiers to the sport that see these events a major accomplishment and perhaps even a reward.
Talking numbers, the vast majority of skiers have no shot at a medal yet they attend proudly with fellow skiers, visit the sponsors and cheer on others on the water. (I guaranty nobody is traveling to Texas to just watch the top 5 from each region ... now there's a party )
Most important to the sport are the younger skiers. Frankly, the more kids you can get to the nationals the better (and their parents will take them). Changing the format to cater to the older slalom skiers could be the final nail in the coffin for competitive waterskiing in the US.
For kids, us average Joes, newer competitors (of any age), bucket listers and locals, one shot per event is perfect.
Now for those that need a bit more incentive to attend. Develop a few more elite slalom divisions that are based on both performance and some form of State/Regional placement. Have those divisions competing through-out the weekend of the Regionals/Nationals with two rounds and top 4 head to head final. If that squeezes the Big Dawg out, so be it ... it is the US Nationals. Perhaps the performances from those two rounds can be incorporated in the Big Dawg 16 (but that's way above my understanding to the Big Dawg format.