Page Editor Question!

So I have been playing with wordpress for some time now attempting to create entire websites using only the wp backend for users not “code” savvy , giving them the ability to maintain there own site.

One of the things ive done to make this process happen is creating a custom site using CSS/XHTML. Setting up the Header.php and Footer.php, and using the Default Page.php to pull my content div.

I ran into the same problem most users have with the Visual to Html editor.

To solve that I simply use <?include (‘Textdoc.php’);?> where i want text to appear and have my clients edit it under the Theme Editor. (which works but is REALLY scrubby!) =/
NOTE: Requires Exec-PHP

My question! Are there any plugins that work similar to the Page editor but will edit a .php file instead of a generated page? ( same thing as Theme-Editer.php but with a WYSIWYG editor attached. )