GunnerZ already pointed out the answer regarding the TCU control.
MaxxECU pro and some other models can control the Toyotal Axxx series of trannies
General settings Transmission Specifies which automatic gearbox to control. GM 4L80E/4L85E GM 4L60E/4L65E Toyota A340E Toyota A341E Toyota A650E Shift mode Specifies
www.maxxecu.com
and not only MaxxECU, iirc the other brands can do the same. MaxxECU is just more open about it. Heck it can even control DCT, DSG and in theres the car with a rojak combination of the BMW ZF tranny being completely controlled by the MaxxECU pro paired with a 2JZ engine. Paddle shifter too. It's damn cool :
There's a full article from Paul Tan about this car too but I don't want to link it here in case they marah like they did last time with LY.
Anyway our cars nowadays are pretty much ancient so there's no such thing as "can't be done" with regards to our old tech stuff. The newer cars however is a different story.