I agree 100 percent with Captainmarlowe here.
1.You can't expect modelers to create 10 high quality models on their own to compete in a competition especially if they don't have their own studio... it just isn't feasible and will only cause people to either not even bother to try or burn themselves out and get carpal tunnels. There are only so many hours you can work on a 3D model per day before it begins to cause physical injury!
2.I also agree that when the same people always win it makes the others stop wanting to participate because let's face it then it is just like purchasing a lottery ticket knowing full well you won't anything.
3. The way things are right now... new applicants have 0 percent incentive to want to participate. The amount of work required to compete is too great and the chances of them winning is too low.
4. You could try a 3D printing challenge where everyone who takes part and is able to create a fully functional 3D chassis for Arduino operated car or a robot body for the new intel servo operated robot would get one 3D printed and sent to their address regardless of whether they win or not.
There aren't that many modelers capable of performing such a task so CGT would only have to print out the successful models which will probably just be a hand full and then give away a prize to the winner of the competition.
This would be beneficial because even if the 3D modelers won't be able to sell their model on 3D websites at least they would have created something unique that they can sell on ebay, amazon, craigslist or even do their own garage sale.
In other words once 3D models become actual objects your ability to sell them increases exponentially. Just look at Disney!
Most of their revenue comes from selling their toys!