The maximum wave we could face determines what we have to design for. If we could be sure we never had to face over 25 foot waves we would not need to design for 100 foot waves. This would make things much easier. Little birds avoid both winter storms and hurricanes by migrating. I think if we have the right migratory pattern we could avoid storms and have a worst case wave of less than 25 feet.
Imagine each seastead uses a kite and sea anchor or solar and efficient propeller to move in a big circle around the Sargasso Sea once each year. The currents are almost fast enough to do this, so even a slow seastead can probably make it. I am thinking Anguilla, Bermuda, Azores, back to Anguilla. We could time it so that we were in the North-Eastern half of this loop to avoid the hurricane season in the South-West and then in the South-Western half of the loop to avoid the cold stormy season in the North-Atlantic. With computers controlling the kites and sea anchors I think we can move at the right speed to make this happen. I think if we checked historical information that doing this you would never have had to face even a 25 foot wave in the last 100+ years. Designing/building for 25 foot waves is much easier than designing/building for 100 foot waves, so this type of migration could make the seasteads much more affordable.
On the edge of this Gyre there is dependable wind. In the middle it can be calm.
If the radius of our migration path was 800 miles, and it were circular, the circumference would be 2*800*3.141592=5027 miles. Over 365 days that is 13.77 miles/day, or about 0.57 MPH. The surface currents are a bit less than this. However, down 100 meters the current is 4% of surface speed. So a spar or sea anchor will work against slower water. In any case, movement relative to the surface current could be very slow (maybe 0.3 MPH) and as you go down the relative motion will go up to about 0.57 MPH.
For the seastead designs that we have talked about so far, I think kites could move them at the needed average speed.
Climate and power usage
This type of migration keeps the seastead in a comfortable climate all year. Heating or air-conditioning may not even be necessary. In any case, it reduces the power requirements for heating/cooling which can be substantial in some climates.
Dodging bad weather
If you have the ability to move, even slow movement can be enough to get out of the middle of a hurricane's path, even if you start there. These days you can get 5 days warning for a hurricane. If you can move 2+ MPH then in 4 days you can move over 200 miles. This should be enough to reduce the maximum wave experienced to less than 25 feet. If you are on a route that should not have hurricanes or storms, and have the ability to adjust the route some based on the weather forecast, and can handle 25 foot waves, you should be safe.
Over time I expect weather forecasts to reach further out. Like in 20 years they might be able to give you 10 days warning.
Some seastead designs may need to count on mobility and some may not have it or need it.
Access to land
This migration path would also mean that at many times during the year shopping or taking on cargo would be easy. This route passes near Anguilla (and other Caribbean islands), Bermuda, and the Azores, Madeira, Canary Islands, Cape Verde Islands. Depending on the type of seastead, it could pull right into a harbor or just anchor offshore while people used a boat to go to/from land.
This makes it easier to meet with landlubbers too. You could meet them on the island or they could visit the seastead. Tourists could visit for a few weeks to a few months depending on which leg(s) of the migration they were on.
Note also that it is ok to get a bit ahead of the migration and stay for a month at one place, then catch up. Just need to maintain the average speed.
Evaluating route safety
I have checked the potential route in the graphic at the top against my "Pilot Charts" for the North Atlantic.
My charts have contour lines for the chances of waves over 12 feet. The lowest probablility contour is either 5% or 10% and the places/times on my route are always less than the lowest contour line.
My charts also have chances of a gale. The places/times for this migration show the chance of a gale is 0% (they note that 0% means closer to 0 than 1% but maybe not really 0). By "gale" my charts mean at least force 8 on the Beaufort scale which might be just 18 foot seas:
It is at force 9 that waves start breaking in the open ocean, which can be particularly hard on structures In the open ocean when different waves combine the resulting wave can break at the top portion. So a 25 foot wave might be breaking only in the top 5 feet.
From the pilot charts my route seems safe from hurricanes. But there is more info online. There is a plot of major hurricanes. Can also see plots by year since 1851 (note explanation of color further down on page and availability of storm database for downloading). The hurricane season is from June 1 to Nov 30 but there is some chance of storms outside this time. August through October is the peak period, with 78% of the tropical storm days, 87% of the minor hurricane (1 or 2) days, and 96% of the major (Saffir-Simpson categories 3, 4 and 5) hurricane days occurring then. Can see a maps of probabilities of a hurricane within 100 miles by month.
From this it looks like the route is still reasonably safe.
So this route might keep you safe from waves over 25 feet. But probably should download the raw database and do more checking. I doubt this is the optimal route yet but it gets the idea across.
There is a bit more on this in a thread on the forum.