I believe curvelinear drill was one of the most significant performance innovations, and I believe it was the Garfield Cadets that brought that in the early 1980s. I believe there had been some asymetrical drill in marching bands and pre-DCI, so I'm not sure how innovative that truly was for DCI.
As far as off the field, I believe the national tour in the 70s was a major innovation. I believe Jim Jones of the Troopers was among the first to develop that. Though rock bands, other types of performers, and sports teams have probably toured nationally in busses, I don't know that touring with such a large group of performers and equipment had been done on such a scale. Sleeping on gym floors, etc.
I can't think of any significant innovation in performance since Garfield in the 1980s. Many of the more recent evolution in DCI has already been done by other types of performing groups, so I would not consider that to be true innovation. While there have been many unique effects and props over all the years of DCI, at the moment, I can't think of many that became commonplace throughout the activity.