Yikes! I never considered the cat factor. What a disaster that could be!
What you've done here would be perfect for my tanks, so thank you for the template. I was slightly uneasy during the brief time the bridge was on my tanks, because in order to make it fit, I took off the entire back half of the hinged, glass aquarium lids on both tanks. As a result, my lights were positioned a little precariously above the single remaining strips of glass, and a good portion of both tanks was uncovered. That wouldn't be a good long-term solution. Add a jumping cat, and everyone could be electrocuted as well as cut to pieces.
If money weren't an object, I would definitely have used tempered glass ordered to size, or acrylic. I actually didn't even use aquarium lids as recommended by the video I mentioned here, because they would have been too expensive. I paid about 20 or 25 bucks total for a large, single sheet of glass at the hardware store, and the nice man there cut my 12 pieces for me, for free.
You're right--the glass bridge actually FEELS quite solid/structurally sound when put together. That was actually me with the leak, though--in my bridge made of glass. My problem was that I sealed the pieces in the wrong order. I built the bridge on a tabletop with the legs sticking up (U-shape), and the most important, water-bearing seam (the floor of the bridge when inverted and installed) was sealed last. By the time I got to sealing it, I could no longer reach far enough inside the bridge to spread the silicone for a water-tight finish. I was getting tiny drips coming from the middle of the floor of the bridge. I am reassembling from scratch now in a different order and hopefully will have learned from experience.