These guys are working too hard to make the Shuttle "passenger friendly." The horizontal integration is too much work for too little benefit. The object of the game is to not have to have passengers loaded into a vertical cabin, and then sitting in the Shuttle bay for many hours. The horizontal stack would fix the first problem, but since fueling would have to be done vertically anyway, we're still looking at hours of hanging vertically or loading passengers after the stack is vertical.

The liquid boosters are a great idea, and one that should have been worked into the Shuttle program years ago.

The removable fuselage section is not a good idea either. The Shuttle would not fly properly with it missing, so one assumes that once the segment had been emptied at the Space Station, that it would have to be put back. Making it "ejectable" is probably not practical. I don't think you could remove such a large piece of the Orbiter fuselage at any high velocity in the atmosphere without the Orbiter and the stack having an aerodynamic catastrophic disassembly, which would probably wreck the module in the bargain.

A better idea: A cylindrical passenger module that simply fits into the Shuttle bay--an old concept. Okay, it wouldn't be ejectable, but as I pointed out, that probably wouldn't work anyway. Also, this would not require the extensive structural redesign of the Orbiter that the removable fuselage concept would require.

A MUCH better idea: forget trying to make the Shuttle a passenger vehicle and work up another vehicle, much smaller, that can carry about twenty people without the horrible logistics of a Shuttle flight. Something like a version of the Pioneer vehicle.