I'm not actually convinced a) is the best solution though. For some things it is, but once you work with structured data that might show up in different places

I'm not actually convinced a) is the best solution though. For some things it is, but once you work with structured data that might show up in different places and might be displayed in different ways in those places, it's not always the best. It works for simple pages where there's no real separation between content and design, but once you have text that's transformed to uppercase in one place because of a "text-transform: uppercase", or a long blog post that's only shown as a summary on the home page - editing directly in place becomes problematic.