Ground steering with wheel brakes - Help

Dear All,
Having a fixed wing drone with a trike landing gear set guided with a pixhawk. There are brakes on the two main gears.
My goal is to stop and steer the aircraft on the ground using the brakes (so would have two outputs and break one side if i want to turn, or break both if i want to stop) automatically.
I am starting with the ground steering settings but i am bit lost as it seems that i cannot mix the steering and brake outputs.
Do anyone has experience or idea, how to do it with a script so we can have firmware updates etc without changing the code each time?
Thanks
Andras