Even though it's using actors and not cartoons, if the people are inside cars and moving about, you could get away with so much before people realise how fake they looked.
Ideally, the whole San Francisco area would be remodelled to reflect the ride as as far as I can remember, they never go there in any of the movies and it seems like it's easier to send them there than to change the area about the ride.
Ideally, I'd like something similar to Test Track with a good bit of speed built in. As big as that plot of land is though, you're never going to get up to anything above 40mph. The only possible way would be to have a stretch of track that extends out over the car park to the west of the land and have it move above or below the HE track. You'd obviously have to keep the track covered as to not waste the illusion plus you'd get the benefit of being able to run the ride without the weather affecting it. They could explain the covered track by saying you're in a tunnel or something.
Weirdly, Test Track fits perfectly into the area.
I can see how the coaster idea lends itself to the IP but if Universal add another coaster, I want it to be something that they don't already have like a wing coaster or a RMC and none of them would make sense.