Re-write .litcoffee file keeping markdown intact?

Let's say I have a config file on the server-side of a Node.js app:

config.litcoffee:

# Config

This configures stuff, and allows comments on whatever.

    privateFoo = 'privateBar'

## Public ##

    module.exports =

Setting `foo` equal to `bar` does this and that.

      foo: 'bar'

Now, somewhere else I want to update the config.litcoffee file, allowing comments in the future (if warranted), and preserving old ones:

whatever.litcoffee:

# Some application feature

    config = require './config'
    fs = require 'fs'

    config.baz = 'bunk'

    fs.writeFileSync './config.litcoffee', config, ...

...which obviously doesn't work.

I see that I can use the coffee command to get tokens and such, but it seems like a lot of work to rebuild those and "splice" the new baz parameter in. Has anyone done this? I'd rather not use straight JSON, as I shouldn't have to have a separate README for the configuration.