It will never happen, but I would watch this show even if you took 100% of the competition aspect out. I like seeing the journeys and transformations. I imagine there are many people that would jump at the chance to go on the ranch to change their lives, with or without a prize.
Maybe each person that achieves a pre-determined and measurable goal is awarded a cash prize. The goals could even be individualized to each person - maybe one person wants to lose 60 pounds, one person wants to run a 5k in a certain amount of time, one person wants to fit into a pair of jeans from 10 years ago, etc.
The show could then show us how these people train to achieve their goals via diet and exercise. It could be in depth and educational TV. For a show about "changing lives" and "challenging America" I've always thought it was pretty light on instructional material. We very rarely even hear anything about the nutritional aspect other than the paid product placements.
I'm very active in fitness though, so I would watch this. I'm not sure if it could ever get the same ratings as the current setup, however.