You could just turn the other bomber ships into similar classes to the TIE Defender, with them strong against capital ships and structures and all, basically functioning as bombers just without the class.
Somewhat related, I've noticed that they never seem to build any space station beyond lv2, at least on medium difficulty. The only ones over that lvl are when they're prebuilt on planets the ai started with.
For the record Fett did once make off with a Star Destroyer, but that's beside the point.
I think some sort of fighter carrying ship for the Mandos. Something to add fighters into battle. Besides that, maybe a Bes'uliik starfighter, or a Tra'kad, though not sure how the later could be put to use. The former, obviously would be an advanced star fighter. Just unfortunate that no actual official drawings exist of either. And of course, both fighters are technically past the era the mod takes place in, so if absolute realism is the point, don't bother with the suggestion ^^;
Now, I also think the stealth should be kept. While Mandalorians did generally opt for a straight fight, a policy of "strategic dissapearance", otherwise known as regrouping and attacking again later, was often employed. It ensured their survival really. So I'd suggest keeping that in.
Ok this is odd, I tried again and the bombing runs worked fine.
Well I think what it is was when I had more than one bomber type present in space. If I recall, the run that worked, I only had the cheapest type of bomber in space, sorry for lack of detail.
Basically, whenever I attempt to use a bombing run with bombers in orbit, the game crashes. If needed I can get the list of bombers I had in orbit.
Otherwise the game seems to work perfectly so far, though I've only played through with the Imperial Remnant and Mandos as of yet.