iirc there are already supersonic commuter planes in manufacture right now of different safer and more efficient designs, to replace the gap left by concorde. the concordes are a pretty old design.
the concordes were plauged by design flaws. iirc they also wern't designed very efficiently, so they were VERY expensive to run. this isn't the case with in-production supersonic craft.
supersonic craft are a lot different to hypersonic craft however. the stresses and dangers involved in hypersonic flight are jawdroping indeed. what makes it even more complex is that a hypersonic "cruise" craft has to first accelerate though supersonic speeds before it can engage it's hypersonic scramjet drives to cruise with.
but hey, it sounds like a challenge
but alas, i am getting ahead of myself. the quoted reasons for designing/using a common hypersonic craft are really just to make space more accessable with common space shuttles, not for cruising from L.A. to Sydney (scaring Hawaii in the proccess). when upto speed you burst your hypersonic engines for as long as there's air to be breathed. if the technology is upto it, then this itself may enable you to apogee into space. but if not then a small solid rocket boost wouldn't be astray.
sure it's a lot of seperate engines to carry on one craft, but the savings in fuel weight (as well as cost per litre, sir arabs) outweigh it. also the savings of a simple horizontal takeoff.
common payloads and common ppl can goto space. yay for space.