This is an excellent idea! If some or your participants are indeed interested in participating in research, it would be valuable to be able to contact them when the opportunity arises, so make sure you ask them for their consent to be contacted by meeting researchers in the future. It would also be good to know if they are in a leadership position in their organization that would allows them to make decisions about the whole organization (or a sub-unit) participating in a study.
One little study I’d be interested in doing would be about why the participants started thinking about meetings (and ended up taking the course): what are their previous experiences with meetings and meeting technology? I would also ask them about the course and a bit later whether they managed to change anything in their meetings but perhaps you are already planning something like that for the last session “Six weeks later: what have you achieved”? But if you’d like a neutral outsider to talk to your participants, this could be a way. Since this would be a little ad-hoc research project without funding, I’m not sure how much time I’ll be able to invest, but if you’re interested, we can investigate further.