Thanks for these thoughts, Hazel. Interesting that you mention week 0! In most of our online courses, we do have a Wednesday-to-Sunday period before the course starts which we call week 0, and which typically contains some of the same things we did in TOOC last week, like the arrivals lounge.
With TOOC we made a deliberate decision to make it a whole week, and to blend the course induction/familiarisation stuff with the beginning of the content. It's set up this way partly to emphasise how important we think the induction processes are, and partly to encourage participants to take the time to reflect on the processes at the same time as doing them. The double load can make it harder, though, it's true, and is unlikely to work in less 'meta' course contexts, so I'm glad you've identified the need for a week 0 in courses where medium and message are not so interlinked.