Jeff Schley:
I'm willing to wager you $1 either Brooks or DJ in 6 months could be trained to be able to play DI football for either an Ivy or Patriot League Team; and we'll include both Army and Navy as part of the Patriot League teams. Getting them thru the Admissions Office may take the same effort and practice as the athletic training; however.
The Ivy league is FCS and the Patriot is as well. The Ivy league doesn't even give scholarships so not the same as a DI school.
I'll even say the MAC conference, let's say a Ball State which is a lower tier D1 school in probably the best Group of Five conference the MAC. We have no idea if they can actually run and change direction with agility the biggest asset in paying a skill position for football. Let's take a leap of faith and say they were starters for their high school teams and indulge a bit.
1. Project their position for Koepka who is 6 feet and 200 lbs. His speed will determine his position. Forget about Tailback or Cornerback to start as unless he runs 4.4 or better 40 AND have great agility, change of directions.
He could be fullback, which aren't used hardly at all anymore, maybe a slot WR for offense. On defense he could be a safety or undersized weak side linebacker. To play at Ball State in the MAC which do make their teams based on guys an inch too short or a tenth of second too slow, but with toughness and development his 6 feet, 200 lbs is starting point. From there we need to see a sub 4.5 or better for for safety and probably 4.65 or better for weakside LB. If he is badass tough, he could get away as a weakside OLB in a 3-4 scheme. Basically a weakside safety in that front at his size, but he has to be tough as nails and put some more lead in his pencil.
If he has Julian Edelman like hands and is tough, which are rare even for good receivers, he could be a slot receiver. Again this is ONE guy who we are purely guessing based only on height / weight where he could play. There are thousands of college students 6 foot, 200lbs. why would we say Brooks can run and catch better than them? We can't.
2. Project the position of DJ. Where could he play at 6'4 205? Well the obvious is possibly QB with that stature or outside wide receiver, probably the split end because I doubt he is physical to block at the flanker spot. Now if he plays QB he doesn't have to be able to run that is the good news. The bad news is that QB is the toughest position to play in football in a game. 7 on 7 or just throwing a football a long ways means BS! Get in a game when the bullets are flying and most QB's simply can't perform, which is why they are so rare. The odds that DJ can throw the ball well enough to actually start for a Ball States are slim and none IMO so let's take QB off the table. Rare skill set.
If DJ can run a 4.5 or better he has a chance as an outside WR, but does he have hands? There is a greater possiblty he has hands to catch then an accurate arm to throw as a QB. I believe he plays basketball and the hope here is that typically basketball players put their hands in the right place to catch a football. He doesn't have to be graceful like Calvin Johnson, but some agility is needed in addition to the hands or he would just be too stiff and CB's could lock him down.
In summation in your 2 examples. Brooks probably has the best chance as a weak OLB in a 3-4 scheme provided he is badass tough and can run a 4.6 or better. DJ could, could maybe be a split end if he can run a 4.5 with body control for route running as well as actually catch the ball with his hands.
We will never know, but of the two above maybe Brooks as an OLB. But as we said above this only ONE guy on the entire tour, so Thomas's point about it being broad is certainly off the table as I have said repeatedly. Respect the D1 athlete as they have a very high skill set, it isn't HS athletics anymore.