I am specifically considering a position on the equator about 240 nautical miles west of Nauru in the Pacific. Put it at 0 degrees N, 163 degrees E. Here there is the northern part of the South Equatorial Current flowing at 0.03 to 0.06 metres/sec (0.07 to 0.14 mph) from East to West. It is a very slight stream compared with Gulf Stream say, which averages 4 mph, but it is consistent. Trade Winds also flow East to West but at 5 to 6 metres/sec (11 to 13 mph and up to 30 mph). Again consistent wind, though may vary I think in the Monsoon season. The main reason for on the equator is it is almost cyclone free.
I am looking to get costs right down by not having seasteads or even mooring lines/dynamic positioning motors, but using existing vessels to still come up with a permanent community by providing facilities.
In this case, I am trying to use the sail power that comes with the sail boats to provide some form of reasonable station keeping, so the community is permanent in nature. I also need to have at least pedestrian access between the vessels. Also I would look to have flexible electricity/Internet cables and water pipes under the gang planks.
In the diagrams above I was demonstrating a gang plank system between the bows. To keep costs down I am now considering using the vessel masts to suspend a central plank between the vessels, and then a gang plank from each vessel to the central plank, so movement of the side gang planks is made on the central plank. Tacking complicates this and means these side planks on the hull need to swivel around but could be done with wheels perpendicular to the plank or with a mini turntable supplied.
With the vessels needing to be fairly close together, there is a very real issue of the sails taking air from one another or even just disrupting the air flow, as you have rightly pointed out. Perhaps a very long box-shaped, strong but light central gang plank so the vessels are much further apart.
Another option might be setting the vessels bow to stern, and in a diagonal SW to NE line and later tacking one by one to NW to SW. The gang plank options from bow to stern become interesting, and now there would be public access along each vessel which I was trying to avoid.
The central body or company would provide and install distance sensors for each vessel to obtain distance between vessels, and software for each vessel to use these sensors and tacking instructions from a central computer to override the autopilot and make adjustments to the rudder to keep each vessel in relative position to the next vessel alongside it and which is closer to a lead vessel.
So I am after a low cost means of creating a permanent community in International Waters, but not surprisingly there are some issues. Note there are Equatorial Counter Currents going from West to East against the Trade Winds to provide another option, but this takes you into cyclone/typhoon territory.