Probably easier and more intuitive to normies if all images were just blocked and you can click to show pics each time. Chances are that their following list isn't audited well, and they might even prefer to be more selective about image loading.
As long as this can be turned off via settings and a toast notification told users to do this the first couple of times, sure. We don't want to make things too complicated for non technical people.
Yeah, when the feature is turned on of course. I mean when it comes to familiarity and ease, block all images exists today (Gmail) but allow from trusted users only is not as widely found and relies on your following list to be your trusting list too.