I love the Mac Pro.
Of course, there a couple problems here. Glass is, in general, an insulator. It will not be good for what's basically a very powerful portable heater. On the other hand, there is glass with special formulations that can conduct heat, so maybe that can be worked out.
The main problem, however, would be a visual one-your glass Mac Pro will look like crap in a few months. As anyone who has opened a computer knows, electronics attract dust. Sometimes, they get even worse things. I still remember this fly that got stuck into my original Apple 23-inch Cinema Display, made of transparent lucite. It died and stayed inside one of its hollow legs for days, until I was finally able to remove it. Gross.
This was, in fact, one of the problems with the candied iMacs, including the original Bondi iMac, but especially with the fully transparent ones. They would start to gather dust and would end looking like crap after a year.
But out of the box? This glass Mac Pro just looks absolutely Star Wars droidtastic.