I've always disagreed with the lineage of the ARC and X-Wing... The ARC had a somewhat similar shape, but I felt that the ship's obvious differences with teh X-Wing definitely implied ships for different purposes and such, regardless of what was written about it being a predecessor or whatnot.
It's like the AT-RT being linked to the AT-ST... I always felt like both having two legs was as close as it got. The ARC was sort of similar. It struck me, if anything, as having a relation closer to the Y-Wing (but still fairly distant IMO) or a B-Wing perhaps. The ARC didn't seem, at all, like a superiority fighter, whereas the X-Wing seemed to be the perfect superiority fighter balance.
It's one of those things I didn't like about the prequals though, and I just separate these vehicles ultimately.
Here's another I would've loved to have seen. AT-PT... That should've replaced the AT-RT ultimately, IMO. Why they went with the RT and it's incredibly flawed design of a completely exposed driver, I'll never know. What good would a vehicle like that do for you that a speederbike wouldn't do better, in every imaginable way? I'll never know.