^The point, IMHO, is to CONTROL the hawking output. You get EXACTLY the amount of energy you need. No more, no less. The rest remains stored.
And, of course, that the hawkings radiation converts mass to energy at 100%.
I have come to the opinion, over the last couple of days, that the space between the wings is for transporting large objects --like cloaked listening outposts-- into hostile territory, where they get left to collect data. I suspect the wings separate and open to allow these objects to be larger than the front or back openings. Of course, these openings are pretty darned large, so it's not necessarily necessary.... Being able to use the volume within for towing would also make it easier for a D'deridex to tow home a war prize.
I also suspect the interior of the wings to have the capabilities of an industrial replicator. Thus, objects large and small, needed for whatever mission they're on could be created in situ using local materials.
Furthermore, I believe the vessel probably has two artificial quantum singularities: one in the bottom wing, one in the top. This way, one AQS can be fueled up with gas from a ram-scoop while the other is drained of mass -energy to run the ship.
If one AQS was about to lose containment it would be possible to jettisoned the section of the wing which has the AQS containment facilities so the rest of the vessel could get away.Then, at the next save haven, this section could then be replicated within the wings, replaced in the socket and a new AQS initialized.
I see a D'deridex as a completely autonomous vessel, capable of decades-long missions.
None of this has anything to do with what we've seen on Trek or any of the Trek materials. I am speculating like mad. ...But... If I designed a vessel that looked like this, that's what I would have done.