The Apps for Office API seems to be fairly limited right now to reading from a document and inserting text and images. For insertion, you can only insert data at the cursor point or replace currently selected text. There aren't yet options to move the cursor or insert more advanced document objects. (Although, the Outlook Mail apps are an entirely different story) I think the typical use cases that work well with this API are easier information retrieval while working on a document and inserting images or passages of text.
I was the program manager who worked on the Word APIs. The Javascript APIs were not meant to be a replacement for the power of VBScript. Instead, we optimized design for apps that could be used between various Office products. The only Word-specific APIs are around manipulating CustomXMLParts.