A utility to create internal links?

Hi guys.

How difficult would it be to create a Xenforo add-on or php script that can find predefined keywords in the forum and create links?

Some key features would include:
  • Ideally this would be able to search for posts within a certain date range.
  • Be able to randomly use a set of predefined URLs for the links.
  • Create an XML sitemap and ping the big 3