Interesting idea. Perhaps JM did take her on campus or where she wanted to go, and found a spot that suited his plans when doing so. That his face is not scratched up is some evidence that she did not go right at him that way. She's a smart girl and would have likely bolted from the car or done something if and when she realized he was taking her somewhere she did not NOT want to go.
The thing that concerns me about that theory, is the report of how incapacitated Hannah appeared to one of the last persons seeing her as she left with JM, and how JM took the time to get 2 drinks before leaving the mall with her. Why would he buy two drinks, when he "caught his fish", as impatient as he is? I think he wanted her knocked out for the ride.
I think the UVA campus and the areas nearby have been thoroughly searched, and dogs brought around there from the very beginning. Now LE is radiating outwards. She's not native to this area, and UVA undergrads tend to stay close to the campus--even the mall area was not all that familar to her, and as UVA posters have outright said, is not a usual venue for the undergrads. JM, on the other hand, grew up there and drove a cab even, so he'd know the intricacies of the area, and being a fisherman, a former member of the Outdoors club and noted for knowing the outlying areas, would likely know all the places less likely to be found.
I hope Hannah was not consicous if she were harmed. That little bit could be comforting to her parents, her loved ones. Bad enough to have to endure her being missing, think of what could have happened, and be waiting, waiting through this search. I keep checking whether anything has been found to help find Hannah.