I love the idea of running training in an agile manner. Back when I was teaching I did something a bit like this. It seemed to work a lot better with evening students who had chosen to attend the course for their own benefit rather than the day students who just wanted a government handout and the quickest route to a qualification.
My approach was to list out everything remaining from the syllabus at the start of each lesson, and get the students to agree on what we should cover that session. I found that I still had to guide the learners quite a bit, though, as they found it difficult to choose between a bunch of things they knew nothing about.
I hope it works better with workplace learning – where the learners typically come to the course with some knowledge and a better understanding of what they want to gain from the study.