Considering the people involved and the nature of the list, I suspect that adding a new @python.org mailing list would be better than discourse. In my experience, it's very difficult to just follow a single topic on the discourse, and most people complain that the e-mail integration is not great. For something like, "Here's a head's up about something affecting distributors", I don't think Discourse offers much in the way of advantages.
My guess is that distributors would be happiest with a relatively low-volume e-mail list that would point to discussions happening elsewhere (or that announces changes relevant to distributors).