The pirate base layout is in GalaxyScenarioDef:
planetItemsTemplate
templateName "Template:PirateBase"
You can add/delete items to make it as big (or small) of a deathstar as you like.
Pirate raid strengths and ship weighing/selection is in Gameplay.constants:
pirateRaidDef
arrivalDelayTime 6.0
minSupply 1
maxSupply 220
strengthPerOwnedPlanet .10
strengthPerCargoShip .0025
strengthPerBounty .00003
firstWarningTime 900
normalWarningTime 780
minSendRaidTime 30
maxSendRaidTime 90
raidStrengthThreshold:0 0
raidStrengthThreshold:1 .25
raidStrengthThreshold:2 .45
raidStrengthThreshold:3 .7
raidStrengthThreshold:4 .9
pirateRaidComposition:0
... and on and on for a while longer, specifically the different raid compositions.