It really is unfortunate that they haven't got round to creating models for Neimoidians in the Confederate Navy, or even pilot droids. They found the time to create specialised droid fire crews who can't even operate the machines they were built for, in other words, just for a few cheap giggles, but they could not be bothered to recolour a regular B1 and replicate it. One hand-wave of an explanation is that the Providence-class ships are built by the Quarren, whose concepts of ship standardisation are not the same as Kuat's. This could justify any discrepancies between the TCW Providences and the Invisible Hand. They're all part of the same Quarren ship class, but nowhere near identical, even in their basic layouts. Meanwhile, the Republic/Empire's star destroyers are all identical to other ships in their respective classes.