I too have been stymied by the TypedInput fields NOT allowing access to "the complete msg object", like the debug node option... in your case, it would be nice to be able to use a
change node to set a global var to be the incoming msg object, or define the whole msg object in an inject node.
In the meantime, I don't see why you cannot do this in a function node:
... but tbh I have not tried it -- and i'm not sure whether reusing it later with its internal fields intact (e.g. _msgid, req, res) is even a good idea. But hey, I can only load the bullets... you'll have to shoot your own foot. ;*)