lazybones,
I am indeed extremely cynical as to the commercial viability of this aircraft. (I think that Boeing has rather lost the plot). However, the reason I created this thread was to question the technical viability. It's an interesting concept, in itself.
The answer so far is that the aircraft may well be technically viable... although there's an awful lot of lose ends.
Can anyone answer my earlier question as to whether localised hotspots of supersonic flow, here and there, would create sonic booms?