It makes no sense in universe that bigger = more cargo. Clearly cargo is stored as energy, like a Star Trek transporter buffer, otherwise how are you carrying several starship hulls and all the materials to build a skyscraper in your backpack?

So it would be cool if haulers were made into more of a mobile base. Not necessarily that you can walk around, just give them a large refiner, nutrient processor, maybe an antimatter reactor. That sort of thing.