Been talking to Chris and some others about this and the main suggestion is like what a few people mentioned here; some sort of virus (EMP Virus or just Virus or whatever), though rather than it doing just one thing (which would become predictable) it can do a bunch of different things - so you can learn what can happen but won't know until it hits you.
Inverting steering (as suggested here);
Flipping the camera upside-down;
Immediately/constantly spamming any and every weapon you pick up;
Locked acceleration, no braking (as suggested here);
The suggestion is that it should still temporarily disable the shield, to make an EMP/missile combo still effective, and it should also have some means of a distortion/obstruction on the screen (glitching HUD/screen elements, noises, weird lights etc? dunno). There could maybe need to be a particular 'tell' for what effect it's had on the car, though (i.e. red shock effect on the car = inverted accelerate/brake, blue = inverted steering, green = weapon spam, etc) so there's still some way to tell what's going on and adjust quickly.
I don't know if it would still be a global effect, whether it launches at the car right ahead, launches at 1st, launches at 1st-3rd, etc. Just an idea for making the EMP into something that's still annoying and doesn't instantaneously crash you out on some of the racetracks.