Throwing a rookie QB in there probably won't be the answer either. Look at Bortles and Bridgewater and Manual, etc. This offense is designed for a QB who doesn't make critical mistakes because they just don't throw the ball that much. When it is time to throw that 3rd and long or the even rarer attempt at pressuring the defense, they need a QB with some semblance of accuracy and good decision making.
When Mariota and Winston have had to face that...on rare occasions in college, they've looked just as bad as Bridgewater, Bortles, Mettenberger or any of the others do now.
My point is, trading UP to get one of these guys would be foolish. If they fall, okay it's worth considering but no way can this team afford to spend multiple picks to get any of the guys who may not even be coming out.