I haven’t really looked lacinia yet, but apparently some people here are using it. Do you think it would be feasible to use lacinia to expose content stored in jcr. There is great interop from clojure with java, but I’m a bit worried about the data types, as they are defined in the jcr, so probably have to translate them in a lacinia way.

Lacinia is biased to assume that scalar fields map to Clojure hash map keys. With JCR I'd presume you'd be getting JavaBeans with accessor methods. The (bean) function would be helpful (though I'd be sure to do some performance testing!).