I've put an advanced registration system in Mihini's RPC system, which sorted between objects to be sent by value, and objects to be represented remotely by a proxy. It's available at
http://git.eclipse.org/c/mihini/org.eclipse.mihini.git/tree/luafwk/rpc.
However, I'm afraid the result is overkill for many use cases, including ours (we ended up piloting Mihini through http/json/REST APIs: all standard, no need for special client-side tools, no wizardry to understand nor maintain). Hence the learn-from-my-fail advice about resisting any over-engineering urge :)
