Far from simple. Getting a PC card and DOS to talk to a modern PC - no chance. Good chance of bricking the car if you get it wrong too. Remember how forgiving DOS was!
What if they just upgraded whatever is in the car?
Reverse engineering could work but It would ruin a classic, iconic car. Some things you just alone.
Cost. You have also got to get all the various other bits in the car to work with a new ECU. Probably as near as impossible as it could get, all in a car worth $millions. Would be very easy to end up with a static museum piece!
It's very much like F1 cars from the 1990's / Early 2000's with similar archaic laptops required to even run the engine. Williams FW14b - FW15c all had active ride setup from laptops that are very similar. Pretty sure whenever they run them these days (rarely) they run them in passive mode.
The biggest risk you have is getting just one small bit wrong and then you have a non functioning car if you are not careful. Even simple things like processor speed (too fast) can render software non-functional. Windows 95 will not boot on a CPU faster than 2.1GHz for example, or with too much memory. Remember ISA cards and interrupts - modern stuff just doesn't know where to start with all that. Emulators can sometimes get things working but on a $10m car - I think not!
