I just started playing with the Cataclystic expansions mod and it added a few new nations. One is kind of crazy with it's main defense building that is... just a little to tall.
It's main ship is rocket powered and therefore very fast. They can cover a large map stupid fast, but they are pretty frail. Didn't stop them from taking over half the map while I built tall.
Main reason I grabbed the mod is it listed commerce modules that reduced maintenance to negatives. Things like trade storage for ships along with farms, mines and workshops for structures. I turtled down into my capitol and only one of my towns, covered them in oil derricks, then built a ton of light ships to take everything around me in one go, and covered them in more oil derricks. Now I'm sending armies of 2-3 Pelican IIs from my last game out to just march and conquer as much as they can before taking to much damage. Not even repairing most of them since I can build 2 new ones every 3 income ticks.
Soon I'll have the heavier weapons and turrets from the mod and the Pelican III will be born. From the ashes of the broken and forgot II's left behind, a new grand army shall arise.