Sounds like a plan.
Here is some information I got off a wooden boat forum.
I'd think something around an inch thick x 1 1/16 or 1/8th wide, would be minimum.
Depending on your skill level, box joint corners with bronze or stainless screws in the corners to lock them would be nice. Alternately, the same size stock with a glazing groove in the center could be used, and edge screw the corners ( the stock would be just mitered corners, like a picture frame). You could set the glass in a glazing rabbet, but, the amount of space left for a retaining stop would be so small that you would be lucky to get 1-2 years on them.
The thinnest laminated glass that I can get I think, is 7/32" thick. A rubber boot around the edge would secure the glass in the frame ( if using a groove). Possibly could bed the glass in the groove with either butyl rubber caulk or maybe an elastomeric caulking ( careful with those, the squeeze out won't take stain ).
Wood frame windshields can look pretty nice, but they can't be overly bulky. Don't want the "home made look ".
Then to answer your other question on sashes, here is what Thompson boats did for there opening.
