Good to be pushing the limits etc etc, but is this really at all close to being practical yet? Just think of the scale of NZ farms vs the DJI range. Unless they can land on remote charging stations dotted about the terrain it's going to run out of power far too quickly to explore much of the farm aside from a brief flyover. Back of the envelope calc: if an avg NZ farm is 252 hectares [2], and we charitably assume it'…
You can keep a Spark in the air almost indefinitely (only landing to swap batteries) with three batteries if you don't mind charging them while they're hot (shortens the battery life a bit) so I'd imagine a Mavic Pro would be able to do as well or better.