The system that Disney are using now is the trackless vehicle used in Ratatouille and Mystic Manor. Cars Land would be awesome but it's more of the same as Test Track. It's also the same problem putting the Indy ride into DHS as long as Dinosaur still exists. I'd like to see more Pixar in the parks before they decide to replace a popular area in WDW with the theme. I'd put Monsters Inc in the area between TSL and RnRC though as I see a huge show building and it's easier to hide back there. I forget who, but somebody suggested putting an Incredibles land in the currently discussed area which I think has huge potential and there's a sequel coming.Galaxy's Edge should have an expansion plot already in place if they do an expansion of the upcoming DHS land.
As for IJA to Dinosaur, I would imagine they couldn't do much due to the showbuilding's infrastructure. Re-theme it, yes; and I would imagine the queue would be where all of the major changes would occur.
As for the EMV system, I believe that the manufacturer responsible for it has stopped making that type of a ride system, so it would be doubtful.
The closest thing to perhaps something newer is like Test Track at Epcot or Radiator Springs Racers in California. But even those don't have the motion base of what is used for Indiana Jones Adventure at DL in Cali and TDS (and Dinosaur at DAK).
I also like the idea of a water ride for the sake of variety.