Very cool stuff. I might have to look a bit more into this. There's a chap melting copper here with a 13 square foot lens - looks like a pretty small beam, not sure if usable for your purposes. But cool idea, have you got some lens dimensions in mind?
Also, definitely not guaranteeing any safety, but think i'll give it a shot.
Sure, I'll work off that copper coin lad's dimensions and try and make it adjustable like the smelter. Could you point me towards an example of the little coffee can forge?