Sure brusselsshrek. This is what we do here

baxter, thanks for the explanation. Now, I see what you wanted to ask.
You are right in some way. But you should understand that any none logged in person (but a real member) will be forwarded to the join page. For example, a member forgot to login and tried to access page for logged members only. And the system will ask him to join AGAIN

So, is it necessary to give admin an option to set document for redirection for none members or not? What do you think?
In any way, baxter, you can change it here:
Filename: inc/fnc.navigation.php
Line: 75
Change: redirect( getDocumentURL( 'sign_in' ) );
To: redirect( getDocumentURL( 'join_profile' ) );