DanB, I think you are confusing different orders of thinking here. People are not libertarian for the sake of being libertarian, but for the purpose of pursuing religious, humanitarian and other strategic goals. So the suggestion that Seasteading be made appealing to non-libertarians strikes me as completely hollow, or missing the point at some level anyway.
The very essence of seasteading is libertarian in that it is a means of achieving such humanitarian, religious, philanthropic, etc. goals outside of state intervention and through entirely consensual cooperation and action. This fact does not contain specific values in itself, and all I’m stating here is that in order to pursue your goals you NEED to be free to do so, whatever the goal is. Simply said, liberty is not a value per se, but a prerequisite – that’s how, as a libertarian, I have always viewed it.
Whatever values you appeal to in order to bring people into seasteading, is really marketing at the bottom line. But it’s still indispensible marketing, that you are entirely right to bring as a discussion point here. Let’s just not jail ourselves into believing the map (the pitch) is the territory (the actual motive), for fear that the confusion between the modus of seasteading and the reasons for seasteading overwhelm us in the end.