My suggestion would be to get in touch with Syvecs / Bosch for an S6 / MS 6.4 ECU or something like this, depending on the car I guess 😉 and start looking for that unicorn that can make a decent map. I also would prefer a Hollinger box than manual shift but I guess that's partly down to what kind of noise suits you.

The key question here would be: Is the ECU Android part completely separated (as right now mostly it is with CAN Bus) from on-board electronics or not? If not well then I know the first thing I wouldn't touch with a torch stick is such a car.

I consider security in cars non-existent yet unless OEMs crypting their engine maps could be considered "security".