I'd like to approach this from a different perspective.
The current perspective is that "chat is good and chat events will draw people to the site." I agree with that.
I would like people to consider topics that they think may be a good source of juicy questions for the site. That is, topics that are deep and wide, and will cause a flurry of research, self-study, and possibly questions on the site.
For example, we can discuss the lives of past prophets, which is well-known and well-documented in hadith. It's also a good source of (mostly academic) questions.
So I recommend thinking along those lines -- chat for the sake of traffic, and also chat that may spurn good questions.