Thank you for your question.
Unfortunately this will not be possible - the reason for this is that Sitefinity should receive the request anyway. If you are storing the files elsewhere, but rather to the place accepting the request, Sitefinity will not even be triggered to process it.
What do you think about the option to create a new web site, which runs on root level, but different port number? Let's say this will be http://root:81. This is possible, just select the root node in the IIS console tree, and click on Add Web Site.
the Telerik team