multi-site web.config files

My group and I are attempting a multi-site setup using a single codebase with IIS7.5. We have defined a ton of rewrite rules using the awesome built in UI. That has left us with a fully pimped out web.config file in our Drupal root. We have several sites already set up, some with their own databases and some that only exist as translated versions of our main site.

How can use new, clean web.config files for each site that would let us redefine rewrite rules (or create local rules only applicable to an individual site.)