What does a draupner event have to do with anything? It’s not like the occulus will be a hole in the roof, there will be glass over it. And I know the seastead will rock and such, but hey, that’s what happens when you live at sea. A big ballasted sphere might roll but it will re-right itself. If we design it so furniture inside won’t go flying about every which way (like bolting the furniture down), only small items will cause minor damage.
As for the mid-ocean ridge, I’m guessing you are suggesting building either over it and finding a way down to mine from it; or saying to build something on the BOTTOM of the ocean.
As for the first one, I can see that eventually happening in the far-off future. By the time we can make it cost effective to mine 2500m below the surface, we will probably have better ways to deal with draupner waves.
As for the second one, I don’t think I’d want to live under 2500m of water where everything outside is pitch black, will crush you in less than an instant, ect…