There is that matter of racing with them. For that, I'd love to see the VGTs not already done up in racing trim to have racing versions appropriate to some league, with alternate liveries, even if PD has to make some up. The GTbyCitroen race car is pretty darn awesome, and that would rock pretty hard, being able to race a WTCC or GT(x) version.
And as for more Vision GTs, this really has been a cool experiment that not many find fault with, and has been an incredible event in both gaming and the automotive world. If possible, keep it going.