Right now CJSON can't include related models in it's JSON output.
I saw in another thread that getIterator and offsetExists need to be overrided.
I guess it would be a lot better if CJSON was smart enough (or had options) to include related models. I think it should include related models that were eager loaded (not lazy loaded) by default.
For Ajax applications JSON format is usually the main output method and returning results including joined table columns is very often required, so I think JSON output with related models is pretty important.