Seriously. People here are way underestimating the costs to develop and certify a major commercial airframe, especially across the multiple regulatory regimes inherent to international flight. You're probably talking about on the order of a billion dollars even if you're playing it cheap. If you want to start re-engineering components instead of buying off the shelf, that number will go uphill rapidly.

This is not a field that's amenable to "disruption". Cutting corners means that dozens of people plummet to their deaths, not to mention the abrupt end of your airline as their families sue you into oblivion. If you try to play this like Uber and flout the regulations, the FAA and EAA will ground and impound your gear so fast your head will spin, and rightly so. Even a test aircraft is a gigantic tank full of explosive fuel hurtling through the air on a couple flimsy wings. When things go wrong people die, and the FAA does not play games.

Airlines are an incredibly low-margin business in the best case, and supersonic airliners in particular are a very niche market and have immense operating expenses (to purchase and maintain the airplane and to slake its immense thirst for fuel). The Concorde's operators could never make it profitable.

Never say never, but this just seems like fantasy. Supersonic airliners are a problem domain that has been pored over by engineers for decades, six engineers are not going to pull a rabbit out of a hat and solve all the technical problems, then get it certified, then start an airline. Each of those is a problem that requires a national-scale corporation to handle.