An idea for a ship component:
+10 max cargo size (or the name of the max size for ship components) as an attachment for 50bc
it could be linked to hull design techs as an equipment pod, with higher cargo space and cost with each design level:
+5 cargo/30bc
+10 cargo/50bc
+15 cargo/65bc
+20 cargo/80bc
+25 cargo/90bc
basicly as the tech goes up, the cost of each cargo unit goes down, but overall price goes up
cargo to price ration:
cargo:bc
1:8
1:5
1:4.3
1:4
1:3.6
The AI might need some more code to handel this (so it doesnt design ships that cost 50,000bc but still can design something useful for a decent price)