JR has no chance to be a decent college QB in my view. Im not a medical expert by any means, but he is immobile to an extreme degree.
That means he has to depend on his passing and analytical skills in order to quickly and accurately instantly recognize the pass defenses and which of his receivers is open and then put the ball precisely in a very tight and narrow spot.
None of the above qualities and QB skills apply to JR. He can't do any of them well. In fact he can't do any of them at all, in my opinion.
JR's strength in High School (prior to his injury) was to be a Trevone Boykin clone and run around like a crazy man with great speed and great moves and make plays on the run, none of which he can do now.
His huge weakness in High School was in recognizing defenses and putting passes into tight windows, which he never had to do because he had All-World WR TERRANCE MARSHALL who caught any ball that was merely in his general Zip Code, which made JR's mediocre to poor passing ability look waaaaay waaaaay better than it actually was.
JR's running ability is what made him a 4 star QB in HS. Not his passing. Colleges loved his scrambling ability but thought (erroneously) that they could improve his passing. Now, all JR has is his passing and unfortunately for multiple reasons he just isn't a good passer at all. Sad.