the Maclin/Davis/Colbert parallel tells me you still have a long way to go. Anyone who's seen those guys play won't buy that comparison for a New York minute.
The comparison is
talent not playing style and etc.
If so, I still think it's off. Maclin is on a plane above those two. Even the most loyal USC homer would probably admit that they never expected Colbert to become anything more than a Josh Reed/Bobby Wade type at the NFL. He simply wasn't a standout player.
Davis is more athletic than Colbert, but he's not a particularly special talent. He was the second or third best WR on his own college team. I don't think LSU fans felt he was destined for great things at the pro level.
Maclin is a bona fide star. In many ways, he was the focal point of the entire Missouri offense (and there are some pretty good prospects on that team). Ask a Mizzou homer about his skills and you'll probably hear rave reviews.
You cited Billy Beane and Bill James, but I think it raises an important point: football isn't nearly as objective as baseball. In baseball, the hitter's job is pretty simple: get on base and score runs. When the hitter is up to bat, he's up there all by himself. Whether or not he fails or succeeds depends almost entirely on him and him alone.
That's nothing like football, where every play involves 22 players and a player's goals on any given play vary wildly depending on his coaching staff, his team, and the game situation. A good quarterback can improve your stats. An aggressive system can give you more big play opportunities. A conservative coach can cripple your effectiveness. A particular gameplan can exclude you almost entirely. There are so many variables at work that it's very hard to look at football stats as an objective indicator of a player's performance. So while you can generally conclude that a baseball player who hits .230 is doing terribly, you can't look at a wide receiver who catches 40 passes in a 16 game season and conclude the same thing. In fact, he may be playing exceptionally well. He may just be the victim of circumstance whereas someone who catches 80 passes might simply be the beneficiary of a friendly scheme.
You can look at combine numbers and stats all you want, but that doesn't mean you'll ever be able to connect the dots and find a way to objectively analyze a player's football ability. Chad Johnson is 6'1" 197 pounds. Reggie Brown is 6'1" 196 pounds. Chad was the 36th pick in the 2001 draft. Reggie was the 35th pick in the 2005 draft. Does this make them identical?
Combine numbers only tell part of the story and football stats aren't a very accurate indicator of performance and potential, so I think you have very tough sledding ahead of you if you want to devise an objective system that will yield accurate predictions about prospect quality. It's a nice idea, but I'm not convinced that it will ever be more effective than a keen set of eyeballs armed with a good amount of knowledge. Where a piece of paper says Jeremy Maclin = Keary Colbert, a set of eyeballs can immediately dismiss that comparison as ridiculous.