Hope my answer isn't too far out of line with what Dave meant, since I feel I get what he's saying.
Not including the Standards wouldn't have doubled the Premium car count. It probably would've added a handful of Premiums. All of the assets were there; it was a matter of updating textures and adding in this new, odd melted-butter damage model. It's a fair assumption to think without Standards, the Premium count would be higher, sure. But not double. Standards (most likely) didn't account for that many man-hours that 200 Premiums could've been made from it.
I agree with a few people who have mentioned that, going forward for the series, PD would be wise to trim a few of the cars on their quest for Premiumization. The Xsara road car in the game, for example, is not historic in any way, since it really has very little to do with the rally car, and isn't even the VTS! I wouldn't mind seeing the focus shift back towards more affordable, everyday sporty cars; like has been mentioned, there's a very limited modern hot hatch selection in the game, and even a historical look back at the segment yields spotty results. The German companies are also sorely lacking both from their sporty sub-brands (M's, AMG's, and RS'), and the more down-to-earth core models. Even the Japanese selection is drying up in regards to new metal; it's the "usual suspects", the big names like GT-R, LF-A, and hybrids, but part of the fun I had in GT1 and GT2 was finding the frankly awesome JDM cars like the Chaser. JDM weirdness is now seemingly up to Suzuki and Daihatsu.
GT2 had a lot of cool cars that GT3 dropped when it made the move to the next generation. GT4 rectified that count with arguably a far more diverse swath of the automotive realm. Sure, a few fan favourites have never returned (Alcyone, first-gen RX-7, 90's Cosmo...), but we did gain a lot of other interesting makes and models. I wouldn't mind GT6 doing the same; ditch the last-gen stuff, bring over what you can, but explore new avenues.
I *do* appreciate the Premiums we currently have, since I like a large portion of them. And I can understand if maybe Kaz is reluctant to get rid of the older Standard models; there are a lot of good cars there. But at some point you do have to start fresh in his line of work; Standards can still look pretty good (as one of the Range Stormer shots showed), but because of how they're modeled, they're just not able to do what is quickly becoming more expected in the genre these days. GT doesn't exist in a vacuum; it does have competition, very serious competition, something that GT1 didn't really have to worry about. Adaptation is key here, and while PD has stayed strong in some aspects, they need to move quicker in others. I want to see them continue succeeding.