Could only imagine the amount of eavesdropping equipment that would be on a vessel with such a purpose. It would take industrial spying to a whole new level. The walls would talk. Then there's the winter seas. Don't think I'll see this in my lifetime, but it's good to see people dream big.
Those floating cities, which slowly drift around the world and promise to visit the hotspots around the globe, come above the surface from time to time. They try to collect money from investors and submerge again. None of it ever became reality. Like you said, let them dream (and dont spoil your money).
Would probably be cheaper and faster if they bought a large second hand cruise ship, but such a vessel does not have the image they are looking for?