It also looks pretty flimsy and I just hope it doesn't fail with a hundred people on it. I'd be happier if it was braced a bit more, there has got to be one h*ll of a lot of force (moment) tending to bend it down at the base and the more people on it the more I'd be concerned. I haven't seen the engineering drawings, but it just doesn't look safe to me...
I also agree that it would be better to limit construction of anything at the GC.
Brian