You asked about cutting tempered glass? I believe that you can sometimes get away with smoothing an edge or corner with a smooth abrasive stone in a Dremel or equivalent, but it may shatter. To cut it you have to anneal it in an oven to remove the temper first. I'm not sure about re-tempering and I believe you'll find it cheaper to start over. Your best bet is to take your plywood panels to a good glass shop and have them cut new panels, smooth the edges as you want them, and then once done temper the panels. A big shop can usually do them in a week or two. Years ago I had one done for a late '40's Jeep Panel Wagon door glass that was just flat glass, angled front. An Automotive Glass Shop made it for me.