I've done a couple of decks off of the parlor floor of Brooklyn brownstones with glass and wood...on a steel frame. One was with glass block, and the other had panels of 1 3/8" laminated glass. Both were very solid. It's an issue that many of my clients bring up, but few want to pay for. One of my clients had subway style grating installed in one section to solve the problem...not a good solution. It's possible to make an entire glass deck...you're only limited by your budget

steve

I saw a house in a book recently that had lexan decking (planks) is a second store hallway to allow the light to pass thru to the first floor. I'll look for the article and see if I can post it here. I would think you could do something similar over that area.

I checked and it is in a book called Beach Houses from Fine Homebuilding. It was sandblasted lexan (so it's opaque).