add "large cargo" to databases(db/upgrades_db.java) and on pass turn or somewhere else, check if the upgrade exists, if it does change cargo limit (in player "cargo_limit" att)to 2000 .
I put this as something anyone can code (don't worry if you think it clusters pass turn I can always refactor it later).
if your a beginner do this one it's super easy.
add "large cargo" to databases(db/upgrades_db.java) and on pass turn or somewhere else, check if the upgrade exists, if it does change cargo limit (in player "cargo_limit" att)to 2000 .
I put this as something anyone can code (don't worry if you think it clusters pass turn I can always refactor it later).