Yeah, maybe go back to lanun workers doing it with a spell, even if its from a ship on the water. (That way you can have units and hammers sacrificed, go a across the ocean, and not have to dedicated a ship to go over and be destroyed.)
Also, the use of pirate coves as far flung bases is a good idea... as for balance, the enemy pillages them.
Another change I'd like to see is them <bactascity>1</bactascity>'d and made a land improvement that doesn't actual change the base terrain, graphics aside... Of course this may require various python checks in any spell to see what land it is on and whether to change the grassland to 'grasslandcove' - a piece of 2 food some gold land that looks coast and the lanun get +1 food from.
-Wait, can land units enter cities placed on water?
- Has/could Xienwolf ma/de/ke a lil' sdk mod that does this a lot more tidily?