Building an aircraft is not only designing new systems and engine mounting points, including a 1000 hr test/certification flight programme (maybe 2 or 3 billion euro's/pounds) but more the construction of manufacturing templates and factory stations, which is another so many billion. When they thought about resuming production of the Fokker F-100/70 after 15 years of closure, they came acros the same problem. That project never matrialised. But I agree, it would lighten up the skies.