Haha my drawing sucks.
Yes I was thinking of using one of those boxes for the waterfall. I'm not sure what the skimmer does, I know it collects debris floating in the water. But if I also use a skimmer I would have two pumps? So instead of a circular flow (down the stream, loop back through PVC) I would have two opposing flows no? Or do you mean the intake of the waterfall pump would be inside the skimmer box?