That's a really good idea Ben, if you use matte paintings in combination with the helicopter to build the set you'd show off some great skills. Like with your challenge entry, work towards that and you should get a reel that flows really nicely. It would tie all your skills together and you'd get a red line in the whole thing. And then you could do a breakdown of the scene to show all the different elements present.
The lighting challenges are on cgtalk under mini challenges. They always have one running, and it's fun to read through the old threads for the comments and to see how many great different entries you get from a scene. You should join one might get you back into lighting
It fits in better with matte painting than modeling I think.