without adding fuel to the discussion about limiting fleetcaps - heres my quick'n'dirty working solution
fleetcap based on tactical/logistic development of a planet :
change the constructor entities slotcount to a negative value eg:
basePrice
credits 200.000000
metal 20.000000
crystal 10.000000
slotCount -20.000000
i also increase the costs of that ship to balance the gains !
fleetcap based on trade / refinery network & safe trading lines :
trade/refinery ships entity changes
basePrice
credits 200.000000
metal 50.000000
crystal 25.000000
slotCount -2.000000
btw. having more developed planets and being able to hold em for a while shows skill and is rewarded with numbers now !