We discussed the weight issue a little bit in another thread related to this build. It should be possible to remove 500lb+ of stuff, and the cage probably weighs ~150lb, so there will be a significant weight reduction. My guess it that it probably weighs close to 3100lb...
If Turner can't put a proper cage into a street car, and do a track build, then I don't know who can, so I don't get the "cage is make belief" comment at all. Who really wants to be pushing an uncaged 400hp car on the track? And, what's "ridiculous" about the window net? It's required safety equipment in most racing series, and this person seems to be planning to race this car. Even if he doesn't, it can't hurt to be safe. What's next? People will say the harnesses and seats look funny?