I don't think so... at least not if you keep the file names the same. The problem is that once you have an extension script mapped it'll always go to the script executable. Unless you re-route the script executable (which is easy to do with a web.config setting). For example, in IIS 7 you could set the handler to the StaticFileHandler.
You can basically map to the static file handler like this:
Comment out the real scriptmap and the point at the static handler. When you're done you comment out the static handler and re-enable the original. You can potentially do this from code since web.config is just an XML file.
One more thing though - if you use a script map that's not standard (like wwd) you'll need to add a mime map so that the static file handler will serve it:
http://technet.microsoft.com/en-us/library/cc725608(v=ws.10).aspx
Of course all this means that the file needs to exist. it would be fairly straight forward to capture response output and write it to file, but figuring out WHEN to write it out might be a bit more problematic...
+++ Rick ---