If they get combat not sucking(you can actually do something to attack support ships) then a cargo hull is very risky as it has nill hitpoints.
It's also a terrible use of resources, if the AI is building cargo carriers, it's stupid. A medium hull costs 26 instead of 20, has 6 times the hitpoints, and 15 extra mass. It's a far more powerful use of the same 5 logistics a cargo hull will take. The extremely slight economic advantage is more than defeated by the 25% extra mass allocation and 500% extra hitpoints. No matter how you're going to utilize them as a combat ship, even if the intent is for them to never take a single point of damage, a medium is still going to be superior.
Cargo hulls are for ships you don't want to see combat, and wont survive combat regardless. They're for the consumables, transports, freighters, constructors and colonizers. Even using one for a survey ship is a bad idea.
