If you just want the expressiveness of Markdown then that's fine, but this is targeted at the same space as AsciiDoc - writing big documents and even books. It's going to be painful doing that without the ability to add footnotes, cross references, figures, notes, etc. etc.

I mean you can do it - look at all the RFCs for example - but they must have been unpleasant to write and they're certainly unpleasant to read.