While hayne is an outstanding athlete I don't think he is any better or worse in terms of athleticism compared to most rookies coming out of college.
So my question is, why would you sign someone without any football experience over someone who has been playing since they were 8 years old. To me a huge part of the game is learning how to read and react without thinking which he may not be able to overcome quickly despite being an outstanding athlete.
I've been watching him since he started in the NRL and he is an awesome rugby league player but whether that will transfer over is a huge question mark.
Good luck to him, whatever happens he will be making history.