We are drafting a spec so this will hopefully happen one day (still a work in progress).

http://spec.harp.io/

I think the big challenge will be with the languages themselves. LESS, Stylus, CoffeeScript, and Jade are all implemented in JavaScript. Finding C implementations would be tough. Though SASS has a C implementation.

If there is a Lua library for it, it'd be possible with the Nginx Lua module [1]

[1]: https://github.com/chaoslawful/lua-nginx-module