I understand what you are asking for but unfortunately this is not possible to achieve with the current version. Major improvements in this area are scheduled for version 3.2.
Let me explain how page templates currently work and what we plan to do to improve page editing.
Controls placed on a template are shared among all pages using that template. In other words, all pages use the same control instance and changes made to the control reflect immediately in all pages. In the future we plan to add control options, similar to control properties, where you can specify that the control will be created as a new instance on the page independent form the template. We are also planning to add role permissions per control, this way you will be able to set whether a user should have access to control properties or just to the control designer (edit content for example).
Your opinion and suggestions on the subject will be highly appreciated.
the Telerik team