I think it all goes back to the fact that colleges couldn't invest the time required to get a QB to that pro ready level. Which was because the NFL would snap them up so quickly in the draft. Which led to the focus on spread attacks, simplistic reads, and athletes dominating moreso than the developed mental side. You still get well coached QBs from some programs of course but overall. It's a cycle that was set in motion by the NFL's greed for QBs.

And the result is these guys need way more coaching when they get drafted now on average. So the NFL has basically forced themselves into a situation where they bought out their own AAA system.

Some coach is going to do what you mention at some point. Might be one of these new college guys on the scene in the NFL. I even predicted McVay would start that this offseason with RPO types like Wolford who are uber competitive but I didn't foresee them getting Stafford. But you're right someone will do it the question is whether it can work. Because NFL defenses are so good, and so specialized, that you're going to suffer vs a team that is balanced and can do different things when a defense shuts down say the RPO.