Admittedly we have a small sample size and the ski league isn't exactly what is being discussed here, but it is really pretty close in concept. Here is what I can say after 1 year of the waterski league about these questions with at least a little data:
1. Current tournament skiers are not going to stop skiing tournaments.
2. Weekend course skiers are a lot more likely to go try out a real touranment after competing in a "tournament like" setting. Tournaments are super intimidating for someone doing it the first time, even for a good course skier, and having sort of tried out the concept first helps to ease into it. We had lots of league skiers go try out the novice division in a real tournament for the first time and a lot more who probably will try it this year. I believe that everyone who tried out a real tournament last year will now go ski another one this year.
3. Unofficial sets that get recorded somewhere (even if they don't really count) will make you feel differently about them when you are getting ready to ski. Not exactly like a tournament set, but a lot more like a tournametn set than any other practice set. I'm not a super strong skier, but I know it definitely helped me calm down when it came time to ski my actual tournament passes.
4. The honor system will work. Cheaters either get phased out by the handicap system (a handicap that adjusts during the season makes it increasingly difficult to keep cheating on a score) or in the case of scores that would qualify for real tournaments, fabricated scores are obviously not going to do anything to help them when it comes to a real tournament.