I have to agree with most of what is said.!
Best to look at if your ECU already has the option of CC.
Then perhaps you just need to add a switch to the Clutch & Brake and a button to turn on and SET.
Simple, job done and will be as safe as an original.!
Or simply purchase an aftermarket CC addon unit.
But I think that option is only good for old non FBW cars.
Otherwise it is best to look at the OBD/CAN interface and TALK to the car.
Do make sure you drop us a message letting us know how you went.
They still have WiFi in Jail.