Actually thats the nesting chamber. As it was the only way to make that tank air tight. Although it sounds like a good idea, I know what you're talking about, in a sense you could create a slippery lip, I might even order a 30x20 lip for the out world since the vented lip will still fit over the top. Nice idea! you've inspired me to spend more money xDI assume the middle chamber is the feeding station? I can see that you have the removable lid and glass frame that sits just underneath which when oiled will allow opening and closing without being attacked.
The good think about the glass table is that it has metal legs and black glass. Meaning that its very heat conductive but less so than just metal. So it will take a while to heat up or cool down so if something goes wrong ill have a precious few hours to correct it.
Im going to buy a large heat matt to cover the majority of the second layer of glass, so that the whole table gets heated evenly. and im insistant that the heat mat must be black to not disturb the look. Now ive just got to find black coloured blue-tac to secure it down.