This is hijacked from the aerodynamic paradigm shift thread,but is germane to the topic:
We've had 60-foot,articulated buses in the U.S.A. since 1951,so it's a rather mature technology.
A full-monocoque,low-floor construction would allow the low profile body.All the luggage would be in the trailer,allowing about 36-inches of vertical height to be removed without any sacrifice to interior space.
They'd be harder to tip over in a collision,and MPG would reflect the lower CdA.