This would be a nice effect! It’s technically doable I think, but unfortunately as I already mentioned, any glass block that doesn’t have a frame would be completely invisible. So if you made a really big pane of glass like this, it would be confusing for people who can’t see the frame when they run into apparently solid air.
They do! More or less anything that isn’t a block does. We haven’t made much use of semi-transparent materials yet but I’d certainly like to do more with them.