Could You Share Experience to Make Your Own Pixhawk Raspberry Pi Drone?

Are you able to do a fine level control from RPi to the pixhawk? For example can you write a python script that would change the pitch, yaw and roll of the quad? Also, if the drone is fully controlled from the RPi, how did you setup the transmitter limits? Lets say its all RPi based and no receiver even present onboard, how would setup ArduPilot? Thanks!