ouright, even easier than i thought, since Json.NET comes with readytouse json.Merge() functionality that seems to do exactly what you're looking for.
so all i had to do was reference Newtonsoft.Json as a dependency to the document:
and then follow the c# demo code for the json.Merge():
mergejson.zip (13.2 KB)
edit: forgot to mention, this works only with latest alphas!