You're assuming I said they can just plug and play, just as you seem to assume that Melvin can do what Lynch can do. That offense will evolve b/c that it what will happen regardless over time.
Unless they really think Gordon is Baby Lynch, or at least the type of runner they can ride on, and he's available toward the end of the round, then yes, I agree. But barring all those what ifs, then it's likely they evolve their Offense in a way that maximizes their talent, including Wilson's, which is not the case currently. But yes, you're going to make RW the highest paid QB in the league to take a chance on an unproven RB (in the NFL) straight from college.
I'm not actually saying you're flat out wrong, but I think you are making assumptions and dismissing the talent and dynamics currently on the roster and that the scheme isn't necessarily static. In fact, based on your logic of keeping the RB as the driver of the offense with the same scheme, I'd pay Marshawn to be back in 2015.