There are three key things I would add to that.
First of all, it's important to have at least one major debate in each official language. I think that's a given for everyone.
Second, having a variety of formats is important, not just to appeal to Canadians, but also to test the leaders in various debate formats. The debate I moderated during the Montreal municipal election was a highly structured debate organized by the chamber of commerce, and the questions were of interest to the general public and very much focused on public issues. Conversely, in English, the questions came mostly from voters. The different formats, then, put the leaders to the test in different roles.
Third, having debates that focus on various themes is also important. Some people take a very narrow view of current affairs, only paying attention to specific issues such as health or youth. In 2012, La Presse organized candidate debates around such themes as health, and I know they were very popular. It's important to bear in mind that only certain issues interest some people.