I would trade the entire VGT cast for the current IMSA DPi quartet. At least it's true and give us a better pleasure to play.
Thing is though, real cars do take time to build (as it was once said, six months, and three if outsourced), while VGT's and fictional vehicles take even longer (a fictional race car out of an existing one will take a year to build, and VGT's could take even longer, because you have to conceptualize it and realize it through CAD before it gets implemented in the game).
You'll certainly see more real cars quite often, while fictional cars will be occasional, every once in a while.
This is why you can't have Polyphony trade cars for certain ones - they don't just appear magically.
Don't get me wrong, I'd like real cars too, but I also appreciate the fictional race cars and VGT's because of their unrivaled originality, and that's what makes Gran Turismo unique apart from the others, besides a decent selection of real-world cars.
I have always enjoyed the Vision GT programme. It has brought us some incredibly interesting cars and approaches to design etc. There are cars I don't like but that goes for the regular roster in the game too.
The Alfa Romeo and Ford offerings were something I was very much looking forward to, but unfortunately they never materialised.
Same here, and there were some VGT's that I personally liked and really enjoyed driving, from the Toyota FT-1 VGT to the Bugatti and recently, the Porsche.
There might be some that are too challenging or outlandish to drive, such as the borderline sci-fi vehicles (such as the Chaparral and SRT Tomahawk series), and maybe some that I probably don't care about because of how plain they are (examples being the Volkswagen, Mitsubishi, Mini and Daihatsu), but I'm glad that manufacturers are really dedicating their efforts to make concept cars for the series. Another reason why, as a Forza fan, that I get envious of Gran Turismo sometimes.
With Ford, they're still in the project, but nothing has materialized yet even after nine years (and although their Team Fordzilla P1 could be close to a VGT concept, it isn't, sadly), and for Alfa Romeo, I could've sworn they were working on a speedster of some sort?
But either way, I'm looking forward to VGT's from Italdesign and Air Jordan, can't wait to see what they come up with.