There's a "View in CIFS" link in the details page for each document, and I don't think it would be a huge amount of effort to modify the default link for a document in the space view to use that link instead of the URL for the download servlet.
That being said, this relies on the browser handling file:// links containing UNC paths properly, and not all browsers can do this by default (this is what the Alfresco Firefox plugin is for, for example).