"how hard is compiling a bunch of XML ..." - sorry to pick on you, but "I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."

Being built on XML, which is mostly just a syntax, doesn't really say anything about the semantics of display and editing. It's only slightly removed from saying that it should be easy to compile any programming language into any other because they're all just ASCII text files.