Every problem on the planet could be solved by modifying humans to live under high pressure.
by modifying a few key cell membrane proteins humans could live and breathe in hundreds and thousands of bars of pressure, with this we could build cities on the bottom of the sea floor using literally plastic sheet bubbles because a lack of pressure differential. 85% of the worlds real estate would open up and resources would explode.
it would also open up the solar system because most moons and planets past earth (bar gas giants) have subsurface oceans.