yes, seems much more flexible but i am against editing the funk_brush though, making an emp_funk_brush seems more logical and sane imo also make sure its effect can be turned on separately (so you can optimize the command view by only letting the insides render when the com is looking etc that is if it is not already possible within your idea (it is written in a way that i only understand half of your text )
You'll have to add areaportals (the standard ones or windows, you'll have to test it), since you can't just add code to do that. You could also try using func_occluders to help reduce the amount of drawn objects from the player's point of view. Distance-based fade on objects and careful placement of detail would needed to help keep performance at a good level. Why do you think it's a bad idea to edit func_brush? If the standard settings disable the new functions, and cause little performance drop, i don't think it's too big of a problem.
i know, not what i ment but nm it seems illogical, every entity has been made "emp_*" if you would change that now and just edit the existing funk_brush some people will never notice the changes are there while now they can quickly assess the changes that are made by browsing trough the new entitys
