I'm going to answer both of your questions at the same time.
I think what the committee members have to do is find a way to organize a major debate in each official language that leaders cannot avoid, an event that is eagerly anticipated because it is recognized as the most important debate of the election campaign, one that is meant to draw as many Canadian viewers as possible. The debate could be publicly funded.
As for whether to limit the number of debates or make a variety of debates mandatory, I would say that the answer should be up to us, in the media. We should be able to hold 18 other small debates if we so desire; that should be for the media to organize.
What parliamentarians need to do is create a not-to-be-missed event that all the leaders have to attend. Canadians should expect something to happen that evening, given all the momentum leading up to the event.