One thing that is still undecided about the "automatically packaged" part of this document is how often we'll make a container. You point out that we have more commits already than could be deployed continuously -- currently that's handled via the train acting as pressure release. As a first iteration: that might be preferable/might be worth mentioning.
Topic on Talk:Wikimedia Release Engineering Team/MW-in-Containers thoughts
If we need 45 minutes to build/test a new container, and we get a change every 17 minutes, we can't do this on every commit. I think we need to do things: a) do a time-based build/test: every hour, on the hour b) work on reducing the wall-clock time to build/test a container.
My starter-for-ten for this was maybe building an image every 24 hours, maybe at 04:00 UTC (our current trough of new commits). It'd be imperfect, but it'd reduce pressure significantly. However, this also reduces the ability to roll things out to only once a day, of course.
Current limitation is once per week, so once per day seems like an improvement. We could iterate from there.