Ok this was a stupid idea (from a technical point of view), but it was something I thought would be cool (in my headTM) so I decided to try it out. I wanted to have the Guardian portal show where you are going, so I created a special model of the outside of the castle and then pointed the portal at it. After a lot of work trying to make it look good and match it all up to the insides of the building I finally got it working.
OMG it is freakin awesome, the screenshots do the whole effect no justice. As you walk up to the portal it fades into view, a closeup of the outside of the castle and then the camera pans outwards as you get closer to the portal. You can slightly turn the camera left and right by moving left and right and get the whole depth thing of the model. Plus the electric shader effect on the transformer in the first room you can see working correctly through the front window. Need to add some more moving fog/mist layers around the bottom and across the front and it should be complete.
Walking up towards the portal as it fades into view
http://www.simonoc.com/images/design/maps_q3/moteof1el1.jpg
The final view when you are next to the portal
http://www.simonoc.com/images/design/maps_q3/moteof1el2.jpg