It will take time, but I would not say it is a massive job. This site uses a similar approach, as the original forum controls are inherited and placed in another subfolder.
The right question is why would you want to do it - the URL rewriting approach is almost always a better solution, as the physical path is not seen by the end user.
The rule that you have tried in your original post does not work for the "extensionless" URLs (no .aspx extension), and you will just have to adjust the URL rewriting rules to the pages you want to use.
P.S. Please refrain from posting multiple messages with the identical topic to this forum. The duplicate threads will be deleted as they really don't help us or other users to help you.