Movemnet always equates to more money. No way around it. More parts, more complexity, more functionality, gotta run more money!
Please explain why the front lights don't have to be as powerful as the back lights. Here's why I ask: When doing larger shows, I've typically had a 40-foot truss flown front and back and rigged the same. What I had in the front I had in the back.
Now, I get the purpose of the front lighting, and then the back lighting helps cut some shadows and restore depth so the setting doesn't appear so flat, as well as take some of the harshness off the front. But since I had whatever was in the front match the back and positioning was pretty much the same, forgive my being confused.
As far as your description on wash vs. spot, I don't need any clarification there. That makes sense. My Q-spot 150's are more of a spot-type effect, but I use them as a wash when I have to. They don't excell at it, but they can get the job done if literally all else fails, they can "just get by".