People may be able to pay the cost of a simple membership but not a trainer, also classes are at certain times, they may not have the space in their own home to workout to the video. Why couldn’t they bring the video to the gym, ultimately renting “space”. Could have multiple TV set ups, wireless headsets so different videos can play at the same time.
I read your reply to Michael, and the thing that struck me is the question of intellectual property. If you video one of your instructors, how is it protected for their sake?
I do not want to be discouraging but I can see a number of issues that would require resolution. At least you would need to talk this through with a lawyer.