If it is a large mission plan then it would likely be better broken up into smaller parts that can be flown with minimal non-imaging flight.
We have seen the crazy stuff some other apps do and it makes it so adjacent images get collected at wildly different times which causes matching issues. It is best to collect the image as orderly as possible such that any adjacent image is collected with as little time between it and its neighbors as possible. We care more about your data turning out well than staying within a defined boundary.
In the US, technically you do not need permission to fly over private property as it is FAA regulated airspace.