Multiple questions - MAVLink control / Obstacle Avoidance

I am a bit confused about the exact functions of Pycopter, Dronekit Python and other software packages.
I have been working on several items and need some assistance -

I am using a Raspberry pi 3, running SER2NET, wvdial, UV4L and webRTC connected to a Verizon USB 'dongle" to give me telemetry, control and live video over 4G. And I want to add object avoidance radar to AUTO mode.

But I have had some problems:

#1. Some of the later builds of Mission Planner do not support joysticks (even the joystick they recommend). And even if it DID work, the Logitech game controller they suggest has ‘return to center’ on the throttle - dangerous on a multirotor, and several other problems. I have found some simulator controllers that might work, but the PWM output range is very limited (like 1300uSec min and 1650uSec max, for example).

#2. I don’t know EXACTLY how APM/PIxHawk controllers do the handoff between radio input (via PWM or PPM) vs Mavlink. I know that you can ARM with the radio and DISARM via Mavlink and vice-versa, but which one takes precedence? And what happens if one fails entirely (like going out of range, or into a 4G ‘dead zone’).

#3. APM code doesn’t do object avoidance in AUTO mode (which is where you need it the most). I was thinking of using a TEENSY 3.2 to accept the RS-232 distance and velocity information from the radar, and then sending either a Mavlink command or actually feeding a PPM command to change the MODE, do a reverse pitch, move upwards and to the side slowly until the radar said all was clear, and then switch back to AUTO mode using PPM signals.

But there has got to be a better way, given all the tools out there. Could you please direct me to someone who could help?

Sorry for all the big type, but that is what the website created.

I believe “whichever one provided a control change most recently” takes precedence (…for that particular channel).

Your radio failsafe settings control what happens if your tranmitter loses contact with your vehicle, and your GCS failsafe settings control what happens if your GCS loses contact.

I believe the GCS failsafe only takes effect if the GCS has been used to control the vehicle.