Anyways...
With this thing having such high vertical acceleration, it can probably make up for its being so squishy by rising above enemy ships and using the balloon as a shield while unloading double gatflak into them. However, getting behind it while be a massive headache for the Mobula crew. This thing turns like a mountain, so keeping a Junker behind it with a broadside pointed wouldn't be a problem. The only escape would be to drop and rise out of the way.
Also, I change my mind about the crew. Two engineers and a gunner all the way.
EDIT: Changed my mind again. Three engineers would be better.