I would love to see this implemented. ATM I can set permissions to disallow non-registered members access to CMS, blogs and forums. HOWEVER when a surfer clicks through to forums or blogs they get the forum and blog screen but with a small banner across the top telling them to register or login. Having a default screen that's the same across the entire site would keep things looking more professional, IMO. For example the CMS page that shows up when a non registered or non logged in member reaches it shows the box I've attached here. A sitewide call to something like this would be great as we can then manipulate this page to look however we want, ie splash/sales page etc.
If there's a way to accomplish this now, I've missed it.
Attached Images