I think your heading in the right direction and have a solid understanding of what needs to be done. You'll probably want a new modern fan (or two) instead of the vent. They're usually 16x16 so frame and wire for that since you're right here. I use a flush cut router bit to cut new holes. As for the lumber. I could only find crappy white wood in close dimension so I opted to buy nice fir and resaw to get the right dimensions. There are a couple outfits in the US that sell that aluminum for the side and you should be able to get that exact pattern. I think a polished diamond pattern would look good for the serving window hatch. Kinda retro. I look forward to your progress!
