and i must say, i think that you are approaching the whole engine thing from a very well organized perspective...
most of us don't realize that we're wasting a lot of our time messing around with various modellers and trying to get level geometry into a game engine or something we've written in a programming language, and expect it to look good or interact with the game environment...
sure, adding some peripheral geometry is fine, but i've come to the conclusion that the main level geometry should be integral to the engine, seeing as that's what will affect the way it looks in the game...
most of us don't realize that we're wasting a lot of our time messing around with various modellers and trying to get level geometry into a game engine or something we've written in a programming language, and expect it to look good or interact with the game environment...
sure, adding some peripheral geometry is fine, but i've come to the conclusion that the main level geometry should be integral to the engine, seeing as that's what will affect the way it looks in the game...
There are a lot of advantages to using brush geometry, with detail meshes placed throughout the scene. Dynamic lighting, portal occlusion, fast collision, etc. These are things you might not think about if you are just moving a few objects on the screen, but once you start building a more complex simulation, you will quickly run into a lot of brick walls, unless you have planned out the high-level systems from the beginning.
The flashlight isn't a specially programmed effect. It's just a standard projector that has been attached to the camera. You could just as easily place it on a car for headlights, or a spotlight that searches the area. It's the same object type as the projectors that make the dynamic model shadows.