The outside loop was suggested quite a while ago, though it was said that the forces would probably be too much for it to happen well/at all. With a lapbar you risk pulling the upper body up too forcefully while the lower is fixed in place (Look at the boy on Paris' ToT). Use OTSRs and you're putting all the force onto the shoulders, which would be far from comfortable. If you were going to control the speed throughout it may be possible, but then all effect would be lost.
Personally, I'm not 100% sold on the "washing machine" theory as it's been called. There just seems like too much to go wrong. The more I think about it, the more complications arise. Turning 180 degrees wouldn't be too hard. But with a 360 degree roll there needs to be enough strength to lift the track and shuttle back up on the other side. A fully loaded standard EF shuttle has a lot of weight to it. That's a lot of force to be able to turn it back the right way... Think of how much force Th13teen uses to lift the track back up. Add a train and people onto that and you've made the job 100x harder!
An interesting point was raised by someone earlier though which I think deserves a bit more exploring. Someone suggested why does the "special element" have to be at the start? I mean, sure, looking at the plans we're assuming that the long straight before entering the building is the final breakrun, and will be directly followed by the station.
What if that was actually only a long MCBR? And the actual station is at the base of lift 1, just inside the building? Suddenly a lot more could happen in the building. With the station in the bottom corner and out of the way there's suddenly a lot more height available indoors. I wonder if reading into the planning document we may not enter the building on the upper level, before entering a beyond vertical drop. Considering the size of the hole, plus the height of the building above ground level I wonder if there may be room inside for one now. This could then be followed by a few inversions, in an attempt to make up the final number. If I remember rightly, Mystery Mine works in a similar way doesn't it? They have the drop midway through the ride. I don't see what's to say the same can't happen here personally...