Honestly, I think the people who rag on there being so many Nissans, specifically Skylines in GT over react quite a bit. Honestly, what that full image shows me is that there isn't really as much wasted space in the game on Skylines as people make out. Granted you could get rid of a good 10 or a few more cars on the Nissan list that are basically doubles or lesser versions that there's no sense in having, but looking at GT as a car/motorsports interactive museum, most of those cars have some kind of historical signifigance to Nissan either at the consumer level or in some kind of racing.
I see historical value in most of the Nissans on the GT5/6 roster. And with Nissan and PD being tied at the hip, a GT fan should expect there to be more Nissan history in the game (e.i.: more Nissans to drive) than any other manufacturer. However, IMO as a GT fan there is a FAR greater percentage of redundant Mazda Miatas and RX7s on the roster that have absolutely no historical value over other nearly identical versions of the same car that truly are wasted space in any sense.
That said, if Mazda designed a new Miata or RX7, I'd absolutely want them in the game ASAP. Same as I'd love to have a newly designed GT-R or any other car. GT in this DLC age is driving game GOLD with getting new cars and even Prototype debuts like they did with the Vette and M4. It's amazing stuff for car fans. It's just the redundancy I have a problem with. And there's not quite as much of it as alot of "fans" like to accuse PD of. I'd rather have 98% of the cars in GT6 than not.