Regarding the original topic, if the ships were significantly different in stats, I'd be tempted to have two so they could both play in a battle. But since all the ships in a class appear to be fairly interchangeable, one of each should be plenty.

It was easy to justify doing a little extra stocking up via the KS, since the first wave were all great bread and butter ships to fill out a basic fleet quickly. From here, though, I think I can be a little more selective. I might very well buy doubles on the sloops in wave 2, while leaving off some of the first-raters all together...