Deep Space Transport is kind of a dead end for ore hauling.

The only things with bigger cargo holds are capital ships like the Orca, freighters, carriers and so on. Of those only the Orca and freighters can be used in hisec, and only the Orca can open a can (freighters can't access cans AFAIK).

So that's it, for ferrying ore in hisec the Orca is the only option that's bigger than a deep space transport. If you go lowsec/nullsec you could use a carrier or a Rorqual instead - but watch out for pirates!