Add the ability to add a tour for a page without editing that page

Most of the existing applications does not have a tour. Adding a tour to them forces us to modify them.
However, I think we could be able to add a tour for page in a separate module. For example: a tour created by a flavor to present the different extensions that are packaged.
A good solution to do that is to be able to add a tour on a page without touching this page (not adding any object on it).