I had more or less the same idea, but perhaps with the markdown syntax extended (I understand this is a touchy topic since there are various markdown parsers that don't all work the same) to allow for simple generation of form controls and navigation bars/layouts.

E.g for navigation sidebar:

* [Home](/home)

* [Blog](/blog)

etc

For form controls:

[ ] I'd like to receive marketing emails.

( ) Female

It'd be even better if it can support basic CRUD/BREAD operations. Basic CRUD webapp with just markdown, imagine that.