As a producer you can always circumvent the constraints imposed by a software. You can use a "this-is-a-title" tag to make text appear bigger, you can use a "this-is-a-list" tag to make content linear instead of using paragraphs, etc...
What I'm saying is that there can't be a format that isn't hacked and exploited to allow the publisher to do what they want, because ultimately it's their content so they control it. Maybe limiting the existing tags in HTML is a good idea (AFAIK that's one of the strategies of AMP) but reinventing a structured format will just lead to HTML-but-less.
If you want to give control to user, then you have to do that from the User Agent: forbid any publisher-provided styling, allow only certain tags, are going to actually do what you want, instead of inventing yet another format
