I don't think a hump aft would have the volume needed, though it'd be a good start.
Assignment Vigilante seems to be hinting at a fuel deck below the cargo deck, if I read the bow/stern view of the graphic right. That would also explain the absence of a visible launch in that graphic, since the launch bay would then be within the fuel deck, essentially surrounded by fuel tankage. Those angles running from the hull bottom and top to the flanking passenger decks could also be fuel space; my math suggests the combination should be about right depending on the height of the fuel deck.
I see two solutions to the obstruction problem. There's an accessway to the launch running to starboard and a bit aft of the cargo deck doors (which I'd have put another block outward to keep that passage open). One solution is to move the elevator to a port position corresponding to the starboard accessway, so the launch bay accesses run to either side of the cargo doors.
The other is to reconfigure the bay slightly: widen that neck behind the cargo door and assume two forward cargo doors to port and starboard of the elevator and turret instead of one long cargo door. Turret's drawn as 3 meters wide - which seems a bit big to me - so a workable cargo door left-and-right of the turret would need a bit more space than is offered. Or, shrink the turret to 1.5 meter diameter, allowing two 3 meter cargo doors to either side of the turret/elevator. Strikes me as a bit prone to accidents, but they're loading in zero-g, which makes loading a lot more like docking and may mean they're using computers or bots for the loading process.
The FASA version places the lower cargo hold aft, with the Launch parked in front of it. The paired lifts are supposed to meet the passenger access of the launch, and the Launch has a roof door that mates with the forward cargo lift.
I'm having trouble visualizing this. Wouldn't the launch still obstruct the cargo doors? And, if the launch is forward of the cargo hold and mates with the cargo lift through a roof hatch, where is the forward cargo lift going?
Roof door wouldn't work for me - which is not to say it wouldn't work given the canon launch, but I did a variant on the standard cylindrical Supp-7 launch by throwing drives and fuel space into the otherwise unusable deadspace of the cylinder, top and bottom which would occur after running a 3-meter-square rectangle up the middle of the 4.5-meter-diameter cylinder for cargo/passengers/etc. That rectangle allowed the launch to accept a couple of standard 3m by 6m cargo containers (featured in the Subsidized Merchant deck plan), with shelves for smaller packages in the port/starboard curves and some passenger seats forward of the cargo containers. The dorsal and ventral curved bits coincidentally had just enough space for plant, drives, and tanks along the length of the craft. (I then modified the rear by adding a rear cargo door so it could accept the shipping containers while retaining the shelving port-and-starboard to get the most use of the available space.
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I get about 16 square meters to the 4.5 meter circle, 9 square meters, to the 3-meter square, so for every 13.5 cubic meter dTon of rectangular space there's 10.5 cubic meters or a bit over 3/4 dTon in the four curves. With drives and tanks in the top/bottom curves, that means 3 dTons to drive, plant, and tank, 3 dTons of small package space to left/right of the main cargo volume, 8 dTons for two shipping containers, 2 dTons for 4 seats, and the 4 dTon bridge in the nose cone (including air lock, fresher, and two crew seats).
(I considered throwing out the cylinder concept and making the whole thing a brick instead.)
