I was advised to buy the
Mavic Air 2 in this CE country I am in, then hack it to FCC to get at least 8km range (and 8km return to home) on our massive farm (for surveillance) in this CE country
You seem to be set on flying 8 km away, but a few pointers might help avoid over-optimism.
The specs for the
Air 2 indicate a max range of 6-10 km CE/FCC.
That's the maximum distance under optimum conditions (no wind, no interference).
You've mentioned things can be windy where you are.
Flying against any wind will reduce the drone's achievable speed (and distance).
If you are aiming to fly out to maximum distance, you need to work with a safety margin to allow for the unexpected and ensure a safe return.
Pushing things to the limit is a good way to run into trouble.
Also .. the controller for the
Air 2 doesn't have the kind of antennas that older DJI drones have.
It looks like it wouldn't take the antenna reflectors and yagi antennas that work on earlier DJI drones.
If you were to attach lights or speakers, they are going to add weight and wind resistance, reducing range and speed.