I appriciate that tutorial very much, but there is one thing that I do not agree with:
You used the gladiator scene as an example for what you cannot do. It is very possible, if you are talented at working with the HL engine. There are ways of working around the engine, like the end scene in HL were there are millions of grunts. I cheated once and shot them all down with the blue swirly thing, they really died. Of course with the time you have to stay in that scene, I could only do one line of them.
The thing is, the engine may have limitations, but they can be worked around. It is a computer program.
Think of "The Matrix", a movie. They could bend the rules while they were inside the matrix. While you map, think of that, and try to bend the rules. It is possible, but takes exteme mapping skills that I myself don't even have much of. I've been trying to make a swinging rope like in the hit origional game Donkey Kong Country for some time now, and am making some progress finally, but now with HL2 coming out, all these things will be easy (Supposedly).
a Hammer is a tool. Use it right, and you can build a house.