Your engines are basically this on a larger scale:
Right?
If I'm seeing that as 2 stages, then yes; but mine is 6 stages. The only other reason I'd extend the length would be so that having it rotated 180-degrees or beyond is more possible, along with oblong engine angles (which can be applied for some interesting ideas. Like flying backwards if possible (with vert-engines or repulsor-lifts (or equivalent)) assisting, or vastly improved dynamics (90-degree face-down and 90-degrees facing left on the left wing, and opposite that for the right. That thing'll roll (left) rather quickly, engine-assisted; regardless it's size.), of course. Plus, for aesthetic purpose, imagine never having seen such a craft before, and you see those things squirming around (no power behind them). Wouldn't you think this thing is some crazy-huge and crazy-ass dragonlike beast? Think "Ancient Aliens". If you're going to be landing in unfamiliar and possibly occupied territory (tribal most likely), might as well be able to freak out the natives a bit more to be sure they won't stop by to try and kill it.
Reason behind this thought. Well, thinking that thought, and reading some good ol' Old Testament. Those angels described? Those may have been mechs. Just read the descriptions closely. I mean, wings with eyes on them and such? I say those are either energy weapons or shield generators.
On the ballast idea:
I think the concept is good, but I'm not sure if it wouldn't be better to just leave the weight out entirely... Being able to shift a weight like that would apply a force to the ship, but for it to be a large enough force to have a noticeable effect, the mass would have to be a considerable fraction of the entire ship I imagine.
At that point, I suspect be better to just leave it out, improving maneuverability by decreasing the total mass/inertia...
Plus, in zero-g I'm pretty sure the ballast would be useless...
Although... If the ballast itself is a crucial (or at least useful) component instead of dead weight, it could work... although keeping a mobile component like that connected to the rest of the ship could be troublesome.
What axis/axises would the ballast move in?
Well, with regards to that, I was thinking of a series of a few heavy weights per segment (like lead blocks or balls that are suspended/attached to a slider mechanism). Considering my airship design is a bit like a catamaran, it needs to divide the weight so that with both weights shifting on either side can work in tandem shifting the Y-weight forward and backward.
Overall, I intend it to be workable in all axis. All the weights would have to be distributed evenly throughout the ship, of course, depending on the chassis design.
X would be on a single track, and a few (maybe 5) distributed along the main rear fuselage of the ship, and maybe 1 or 2 tracks per front-wing. Of course, all the weights default at center, and those split from the center start as close to center as possible.
Y would have a single main track, and 3 sub-tracks distributed in 3rds so that there wouldn't be too excessive force. A counter-balance, so to put it to prevent excessive stress on the structure. The sub tracks can either support or counter the main weight however. Of course, these also default in their centers.
And Z would be on the tallest portions of the structure and on the edges and center.
Optionally, there can also be a ring-ballast that can be applied using the same principles, except oriented from a primary influence point (usually the center of the ship), each ring rotates where the weight (on each ring) should be placed.
With proper control of the ballasts, and enough re-centering of the gravity, the trajectory of the ship (whether flying, falling, or even sinking in water) can be influenced, even if slightly. This can be a great help to counter some turbulences, counter tailspins, balance the weight distribution to prevent some issues when carrying excess loads, or when sinking, either keep it level and preventing it sinking awkwardly, or miraculously keep it afloat by precision of distribution (sorta like a barge).
And as for semi-orbital, I didn't mean truly zero-G, but even a hard enough slam of the weight (overriding the ballasts' brakes, of course) should be able to make the thing spin a bit and alter it's trajectory. Weight could be a surprising assistant when moving at a terminal velocity, or if you're going at ridiculous speeds, and even the slightest adjustment of the ailerons/elevators/rudder can really screw things up, the weights should help adjust even the slightest direction.
Of course, the system comes with the disclaimer "Do not use unless you know EXACTLY what you're doing.". I think when I was screwing around with this idea, I was inspired while screwing around with modifying some of my cars in Gran Turismo. They have an X and Y ballast system (at least for rally cars) that can really make or break your control/leads. Hell, it even helps out with drifting your sports/road cars. It's surprising how even the slightest adjustment of that can screw things up.
EDIT:
Second-thinking those ring-ballasts, I think those can act as sort of a gyroscopic stabilizer (just keep them spinning), keep it's heading true even in low-to-no Gs. I remember seeing something like that before. Ever see a gyroscope drift across zero-G while (not) spinning? Nifty stuff to make use of there. Just beef up the scaling a bit, and it can probably change the game of extra-atmospheric flight/combat.
Vid Links:
http://video.google.com/videoplay?docid=2052918739541398536#http://www.youtube.com/watch?v=gdAmEEAiJWoJust think, have the 'scopes running while facing a direction idly. Shut off one or two (or all) of them and adjust angle, then re-activate all of them at a position you want to face. Kick the engines online, and have fun hell-dropping. I mean, it should minimize using jet/gas propulsion to adjust angles while in micro-grav.
EDIT EDIT:
Holy crap. We gotta start lowering the word count on these posts a bit.