I can't say my view for the series is different because i also do think the same as you guys, which is correct the flaws of the game, like, standard vehicles (Not get rid of them, but make them premium), sounds, obviously, new cars, track creator and all that stuff that everyone goes on and on about it.
Sure that would be great, but i think that will not be enough to make the game be, what it once was... i think it's time for Gran Turismo to go a bit retro, bring back things that once were in the game. Like, classic style license tests, like they were in GT1... only white vehicles, and use the same car in the same track, like the FTO on High Speed Rind S corners, or the Griffth 500 around Autumn Ring. Bring back more old tracks, such as Special Stage R11 from GT1, Seattle Circuit from GT2, Red Rock Valley and etc... racing modification, even if unreal... like, in order to get the GT-R GT3, you must buy a standard GT-R and apply the racing modification on it, with different livery styles, base model, N24 Schuzle, GT Academy, etc. Classic soundtracks, such as The Cardigans, Garbage...
And something that i'd like to see, but probably would be too hard to make it, would be an "history mode", where you start racing old cars, in old tracks and progress in time... Like, a series of races in 1960, then 1970, then 1980... and each "era", has different races, like, street cars, rally, Le-Mans...
Because i think Gran Turismo needs more than just fix it's problem, that would make it a regular game, and being regular is not enough.