Neil Gould writes:

That ratio isn't all that different from today's aircraft, is it?

Even with ten across, the ratio is 1 in 5. In smaller aircraft it is higher.

Where do the emergency exits go? Which airports will be constructing
completely new gates for these aircraft? How long does it take to replace an
engine? Where do you board the aircraft? Where does the cargo go?

I'm sure that noise reduction alone cannot justify this aircraft. If the gain
in fuel is really 35%, that could work strongly in its favor (it would have to
be verified with real-world prototypes), but probably not enough to overcome
many other issues, only a fraction of which have been mentioned above.