Seeing Gran Turismo as just another racing/driving game - which are strictly limited just to some kind of motorsport-presence - is plain wrong.
Well, the reason I think my Career Mode idea would work so well is that the basic pattern for it is laid out in GT Mode already. In GT Mode, you start out with a small sum of credits, somewhere around 20,000 Cr, unless you resort to a money boost option. That's enough for you to buy a decent new car of moderate performance, a high quality used car of better performance with a small amount remaining which might get you a few upgrades, or an older used car of good performance which can be upgraded much more.
You then enter the beginner races and try to win. Prize money is decent enough, but the real prizes are additional cars. Upon winning the entire series, you usually are rewarded with bonus credits, as well as an additional prize car.
This opens up more races with higher performance requirements and a stiffer challenge. Rewards are higher, prize cars are better, and usually good for entering in the new races. If you play it right, you might not need to buy a car for some time, as you win prize cars which are necessary for certain races. In GT4, I only bought cars I wanted to collect for a few months in gametime, and used prize cars almost exclusively to progress through the game.
Invariably, you'll have to buy a car to compete in a certain race series, or you'll just want to open up and fly in a serious racing machine, and by then, you should have enough credits to do much of what you want. Along with that, the race series will be getting dramatically more advanced, requiring you to have race cars of certain types, though the rewards get much greater at this level.
And on it goes, until ultimately you're racing Formula 1 cars.
Okay, so why even bother with the notion of Career Mode or Season Mode? Well, it's because I want that Next Level in Gran Turismo. It's not just race mod, or a livery editor. Those are very nifty, and very appropriate for on- or offline racing to establish your identity, and to give you some "wow," pride or cool factor. But what Career Mode does is put some real substance or "meat" into the traditional GT Mode. It gives you the chance to be a Mario Andretti, Colin McRae, Michael Schumacher or Mattias Ekström at the very start of their racing experience. You start at ground level with the hope of being one of the rising stars in motorsports. Not because you're the game owner, but because you must prove your worth by competing against a number of other (virtual) drivers, all sriving to win points and attract the attention of lucrative sponsors. This kind of racing arena would give all of us a sense of what it is to carve a name for ourselves in the annals of racing history, as all the great drivers did, by starting from humble beginnings and working our bumpers off to find the winner in each of us and be better than everyone else.
And like I posted previously, Season and Career Mode aren't intended to replace Arcade and GT Mode. They would still be there, and always will. This sort of thing is very ambitious, but would actually be the easiest to design and code of all the ambitious things Gran Turismo might want to be. It would be the same thing as GT Mode, but with leagues, a calendar, racing rules, points, and names for the A.I. drivers.
Someone is eventually going to do this, and I'm hoping that Kazunori-dono gives it to us first.