Kind of a long question, here goes...
Often you here about a player that would have flourished if said player was drafted t a different team. Say maybe if Tebow was drafted later, and to a team that was already set up for a running type QB, or Akili Smith, Cade, Tim Couch and all those guys might have flourished, or at least done better, if drafted to a different team. So what if a player that is in college knows that he is not suited in a certain system (RG3 in Denver's system, or Luck running chip Kelly's offense)? Why cant instead of going into the draft, why cant he just come out of college and choose what team he would like to apply/tryout/workout for. What if (enter top rated college RB Here) was a die hard Broncos fan, and knowing that Denver has a need at RB, decided to forgo the draft, and try to sign with Denver early. Maybe after the college and NFL season instead of going to the draft. Maybe it's a simple answer like more money if you get drafted, or "everyone would be running to winning organizations (see above RB example)".
If those are the answers then fine, but is there a rule that states that all new players have to enter the draft?