Not claiming to be an expert by any means but I don't know if hardboots were the answer today either. When Jacobellis was DQ'd in the semis it was because she lost her balance off of a jump and over corrected on her heelside edge sending her flying through a gate. No way hardboots would have helped there.
I think that if you switched the equipment on everyone in the field you would simply see people falling on different areas of the course. As mentioned earlier in the thread, the rhythm section at the start would be a nightmare. While more people may make it through the banked turns unscathed, I think we would see more wipeouts following each of the jumps.
Also as has been mentioned over and over again, softboot technology has improved a lot over the last few years. I can carve pretty well on a 4 year old Atomic freeride board with some stiff Ride bindings and good boots. Of course it doesn't match up to a hardboots setup in carving at speed, but I'd be a lot more comfortable airing 20 foot gaps in softies.
Just my 2 cents. I'd love to hear from BX riders who have competed in both that can give some more detailed pros and cons