That's an interesting idea, but I don't really see the spokes as cargo or mission modules.
I've always had it in the back of my mind that the saucer shape is there for a reason, probably some kind of giant field coil or accelerator loop related to the FTL drive system. In either case, there would likely be a ring of electromagnets, capacitors or other technomechanical devices running all the way around the rim of the saucer, which is where the idea for the "spokes" really came from. However, there's no particular reason why those components would have any visible manifestation on the contours of the ship's hull, so the logic behind the idea only goes so far.
I think I already have a better alternative in mind, which I hope to show in the next iteration of updates.
As for storage and cargo, that's a good question that still needs to be addressed. At the very least, we probably need some large access doors somewhere. Have to give that some more thought...