With the addition of a new medium pad cargo king (T-8) last year I hope the chances of a higher capacity large pad ship has increased. For some semblance of balance it would make sense that it takes roughly twice as long to deliver double or more goods as a T-9 suggesting poor manoeuvrability & speed, and low jump range (although carriers make jump range moot in many circumstances), that would also keep the rank locked Cutter desirable with it's ample speed & defence.
I think it would be a good match with a carrier for loading, unloading & transferring Tritium to the carriers fuel tank.
For commodity trading balance there is already a mechanism that nerfs the effect of T-9/Cutter large qty trading, that can help offset the effect of the BGS on factions too.
I guess the game designers have balanced stuff like CG targets, station repair & colonisation qtys on commodity availability and time, a huge slow trader wouldn't have to upset that existing balance while still allowing benefits to loading & unloading carriers.
An enormous, well protected turret boat would make AFK bounty & combat bond farming easier so I think a long wheelbase T-9 kind of ship would make a better fit than a fat Cutter type.
I'd love to have the choice for variety. I have lots of exploration ships, lots of combat ships, more choice for cargo hauling would be great.