I had the same idea, do the brass work myself. Unless you have access to a mill, the slot for the switch will be impossible. At least impossible to make it look decent. I had milobender make my plate, and cut the slot, as well as the countersunk holes. He graciously left me the drilling of the control hole locations, because I wanted to lay them out myself. Use good drill bits, you want the holes to be nice and clean, and you wouldn't want to hurt your plate.
I decided after I got the plate that it was much nicer than I could have done on my own, and I was glad I had an expert make it.