The seastead will have 3 columns that are 4 foot wide and go 13 feet into the water at
a 45 degree angle.  There will also be 2 cables from the bottom of the columns to the adjacent corners.
The seastead is about 30,000 lbs I think but this is NOT a normal boat hull shape,
it is more like a tiny oil platform as far as drag.

Normal operation will be with 2 submersible mixers with 2.5 meter propellers
using differential thrust but here I want you to look at different backup ways of moving the seastead

We will have lots of solar but not unlimited.

Lets assume we have 2 of these submersible mixers:
      https://www.shinmaywa.co.jp/english/products/pump/introduction/sm_sme/sm-vrtn.html
      https://www.mrm-shinmaywa.com/filesdirectserver/itp1/z_itp_12042022f9ii/originalz-z721968334010.pdf
          2.5 meters 
          3200 newtons   - (720 lbs)
          Is stainless and ok for seawater
          2–3.2 kW

As the vessel moves the thrust generated and power used drop off like in this table for each thruster:

MPH      Thrust (N)     kW
0          3200         3.2
0.5        2380         2.8
1          1560         2.4
1.5         740         2.0


Please try to estimate how fast the seastead could go with 2 thrusters and 
each thruster using power of:

1.2 kw
2.2 kw
3.2 kw