If I read all this stuff right, you will now be able to modify Drupal's files through webDAV. While this is probably interesting I think that modifying and uploading files to Drupal through webDAV would be more interesting. Eg image module would have an webDAV enabled upload directory and retrieve uloaded files from there.
Indeed, but probably it would be better to implement a webdav(ish) hook, webdav is a kind of file/version control oriented RPC. Drupal does have the nessesary igradients to be able to implement it - XML parser, php knows about post, put, whatever http requests, we have the example of the BlogApi, Webdav is not too different. A native understanging of DAV will allow updating any content by submitting a file via webDAV. The only missing ingredient is http authentication against drupal, that is Drupal knowing and speaking the www-authenticate and authorization http headers. -- Vladimir Zlatanov <vlado@dikini.net>