I think there's lots of opportunity for a markdown alternative, but I worry that this starts in the wrong place. It seems like it's built around code, whereas Markdown is built around writing.

A friend of mine who works at a newspaper noted that it was really hard to get a lot of people in the mindset of Markdown, because it requires users to think about their writing in terms of HTML, which is harder than it sounds for some. This seems like it pushes things further in a direction where people who aren't code-savvy can't get on board.

The other thing to keep in mind: The reason why Markdown is great is because it's readable even without being rendered. This is not, because it simplifies the HTML without abstracting it. That's a tough hurdle to get past for a lot of folks.