For Markdown --> ConTeXt usage, math is not my primary concern, but
wonder what do you think about the Pandoc's "cons" as stated on
pandoc-xhtml site, iow:
* Main document language information.
* Markup for language in text portions.
* Any <div> or <span> elements markup.
For the document language, Pandoc provides language variables:
I haven't tried it, so I don't know if it'll handle variations on quotes or hyphenation, but that strikes me as more a presentation layer aspect than a content aspect. That is, ConTeXt (or LaTeX), given a language, is responsible for showing the correct representation; whereas, Markdown is responsible for the prose.
Intermixing languages is also possible, as per the above link.
Lastly, the above link also shows how to mark up div elements. I'll cover how to create inline images later in the series---it requires a little bit of Lua, depending on the complexity of the problem. See:
Cheers!