Great sounds like something that should be built. Sounds like a job for a country Japan, South Korea, or China that's willing to execute a project over the long-term.
Building supersonic passenger planes was never a technical problem (see Concorde), the problem is: they are too expensive to operate to be profitable. I bet this thing will never see any commercial use.
It is a technical problem bit still with very hard limits as to how much energy it will cost minimum to accomplish. You still gotta push through the air at higher speeds which takes a lot of energy/fuel. Best case is they go high enough to avoid a lot of the air, but you still have to get yourself up to that altitude through the air to start with.
Airplane cost to operate is fuel consumption, and, by the laws of physic, aerodynamic resistance scales as a square of speed, so you can’t really work around it unless you invent some new laws of physics.