The risk-reward isn't there for pirates. Seasteads will likely be well-armed, populated, far from Somalia and other pirate operating areas, and lack the large material payload of a cargo ship or oil-tanker.
have some kind of contract with tugs, lifeboats, helicopter rescue, etc. You could set up some sort of insurance system for citizens/inhabitants to cover those contract retainers.
Hell, you might even end up contracting it out to the Coast Guard if they meet your needs and are close enough to count.