Since I'm not focusing on a floating seastead model, but rather a fixed gravity base structure model, I'm thinking a fixed breakwater system would be best. Something similar to deep water wind turbine systems, using either monopile (b), gravity base structures, (c), or jacketed base (d-f):
I'd aim for gravity base structures due to their strength and stability, and it has been proven to work fine in depths up to 300m. So you have gravity base supports:
Strung out in a line where your breakwater will be:
And you build your breakwater structure in the interstitial spaces:
The breakwater structure can be simple like this, giving some outside recreation space:
Or it can even integrate wave energy systems:
One major downside for this kind of system is that it doesn't scale...you need to build your breakwater at the maximum size you will expect for the future. You can't exactly re-float all the gravity base structures and move them out to increase the breakwater diameter. So that will need to be factored into the build.