The plastic does help, a good deal.
It is possible you saw a 1/4" rimless tank. Is it a good idea to copy? Hell no. People do stupid things all the time. Euro braced a build 3/8" should be fine. I would also brace the bottom if I were you. As mentioned, the thicker glass does more than just prevent bowing, it helps give the silicone something to grab onto. Adding an internal bottom brace adds more silicone to help hold the glass.
And I know what you mean, I love the rimless look as well, that is why I have a 93 gallon rimless tank