I saw around here dendron has taken a look at org-mode as a possible implementation. Have you guys checked Asciidoc? I mean, I love org-mode but asciidoc makes more sense to me for an application like dendron. Has some beatuful features for customization (like attributes in your document) and exports documents in a very profesional way. We use it to write pdf client reports and whitepapers. And I think with ascidoctorjs (https://github.com/asciidoctor/asciidoctor.js/) could be great since has a great API for extending the syntax or parsing features