I think milling chainrings from scratch would be a real pain, but I'm pretty sure you could find a solid chain ring and either etch things into it, or cut chunks out of it, "mill" it if you will. You could do a pretty dope job with a nice dremmel tool and clean it up with a nice file. I've been thinking of doing something similar to an old cottered crank where the outside chainring and the crank arm are one piece.