How about... if it's firing arcs... were primarily vertical rather than horizontal? like alot of guns are currently fixed at a horizontal angle to the ship (to prevent or cause overlap in firinc arcs), how about fixing them at a vertical angle? like the ship is great with dealing with targets above or below it, but has a harder time targeting ships at the exact same level as it.
Doesn't need to fire in a completely straight arc up or down, can still be at a reasonable angle, but maybe tilted by a 5-10 degrees, and in the top and/or bottom of the ship (kinda like how the junker has those below deck guns facing sideways but with an added tilt).
You could then decide to make it a bomber as you said, with 2 guns on the front and back (maybe a 5th gun on the top as an aft-gun (WW2 bomber style, could be like, in it's own little dome))
Or you could decide to make it an altitude-based fighter, with 2 guns on the top and bottom, either both facing the front, or more spread out, depending on how you want the angles and overlap to be.
It's weaknesses would be ships at it's own level, though it could use it's balloons to shield it'self from them while it tries to shift altitudes, should be good for some interesting gameplay.
Downside of this design would be the fact that there's a height-cap, and, well, the ground. It could be negated very effectively as a bomber just by having everyone fly at maximum altitude, unless it also had at least some top guns. If it had only Top-guns it could be countered in the same way by people flying low to the ground.
Medium guns are... a possibility, but you'd have to consider the heavy carronade bugbear which, with an added downward angle will ruin people's day rather harshly. Not that it doesn't do this currently, once you are balloon locked, but it's still a tad easier to get into your own gun arcs than it would be with such a design. Probably don't want medium guns on this thing just for that reason (not to mention that all other medium guns are rather long range, which would be useless on this kind of design cause the distance between max flight altitude and, well, the ground isn't that high, and with the angles locked you wouldn't be able to fire very far away regardless).
So, light guns then. ignoring the amount of guns and bi/trifectas for the moment, should it primarily be a front or a side-pounder? well tbh, if it allready has to do alot to keep the right altitude in an engagement, it might be too much to also diminish it's ability to keep the right range, on top of it being squishy. on the other hand it would make more sense to fix a vertical angle to the guns if they were forced to fire under/over the balloons though, but... maybe that'd make it too similar to the junker? balloons aside the junker is allready a fast, mobile side-fighting ship with a difficult to hit hull and big balloon as it's weakspot, if the only real difference is having to shoot under/over the balloon i feel it's too similar and will be hard to give it's own niche.
So, possibilities to distinguish it a bit more? Obviously there's the front/rear and top/bottom firing thing, but... it could be made a bit more interesting than that I feel. What if we made a single-sided bomber, kind of like a combination between the squid and the junker. It could have 3 (or hell, 4 for all I care) light guns fixed to the left side of the ship, pointing in (close to) the same direction, but nothing on the right side. Maybe add a single front or rear gun for utility/defense. The 3 main guns should be fairly easily reachable too, since the downward angle and single direction would make for fairly brief/easy to lose engagement angles, which shouldn't be wasted on running to the guns.
Ah, I hear you say, but now you've just made a "bad" version of the mobula, which also has 3 light guns on one side, plus 2 more to choose from! And the mobula allready has better up/down movement than regular ships, so you're encroaching on it's niche as well!
This is true, the mobula doesn't have the "downward angle" clause that this ship would have, and it has a bit more utility too. However! this ship would be more maneuvarable, easier to engineer on (components fairly close together) and have a closer tri-fecta on it's guns, allowing for a wider variety of weaponry to be used simultaneously in the direction it's shooting. In general, it would be more suited to quick close-quarters bombardement, than the long-range/utility (and occasional brawling) brought by the mobula.
It would be quite reliant on it's allies to get angles as well, so in a sense it's a close range version of a combination of squid, junker, and mobula, with a unique firing angle and approach to combat (relying on a combination of mobility/positioning and it's dual balloons shielding it to keep it alive)
