[jc173]

You could probably get the AI to build more defense bases by fiddling with the settings in the *construction_vehicles.txt file. Just decrease the number of planets per item or increase the number of must have at least. Keep in mind though this may screw with the AI's strategy since bases are pretty expensive to set up. They are capturable though. I grabbed a defense base battle station and a battle station ship yard Last night from the EEE. Which was pretty ideal since the two stations orbited a world with a resupply depot and other goodies deep in their territory.