Everything people have wishlisted would be great to have.
My biggest wish is for GTR3 to be more like driving real cars, which GTR2 is definitely not.
The response to input in GTR2 (and Race 07) whether by wheel or gamepad is very "abrupt". That is, especially with initial inputs, the vehicle abruptly assumes the direction or attitude that is specified by the end position of the input.
That's entirely unlike driving a real car in which steering input is nicely smoothed out. GTR2 as it is now actually feels more like driving an old pre-power steering high steering lock car (which I have done).
To feel this smoothed out - but still linear - steering in a game, Live For Speed, has this aspect of car control almost perfect.
Second, I think the poor GTR2 tire models and suspension models also contribute to this abruptness. LFS also has this pretty much right and the old Race game (race.nl) had a tire model modification module that did for tires what Engine Shop does for engines.
I think the GTR2 game engine itself is probably capable of handling better tire and suspension models.
The difference between GTR2 standard and GTR2 Reborn is like night and day. The GTR2 Reborn folks concentrated on tire models and suspension settings and GTR2 and Reborn are like different animals. Only lacking in Reborn is fixing the input abruptness issue. (I have spent more hours than I care to admit with steering response, speed sensitivity, slow bump and rebound, wing, steering lock etc. and can make things less abrupt but always sacrificing linearity and responsiveness.)
So, if SimBin wants my money for GTR3 I would of course love to see loads of the items others have wishlisted but the only way they'll get my $40 or whatever is if GTR3 drives like real cars.
To me that means the cars "feel" real, they progressively move toward loss of control (unlike GTR2 standard, Race 07, and old Porsche 911s), and steering input from wheel or gamepad does not produce an arcade-like abrupt change of direction like driving with a mouse would.
If SimBin did this, and GTR3 is playable offline, has a good Nordschleife, and doesn't require a new $1000 computer to run it, I'd buy it as soon as it came out.
Just flashy graphics and some "cool" won't open my wallet...