In a “group” sightseeing flight, I think the ability to add a waypoint from the world map screen and while flying in-game would be very beneficial.
WORLD MAP: the ability to add a Lat/Long waypoint which would then be viewable in flight to view your neighborhood or view a landmark location which is not a “flight sim landmark” would be very beneficial.
IN-GAME: During multiplayer game play, the ability to drop a live custom waypoint marker which others in your group can see and fly to would be an excellent feature. I fly over a neat feature and want others in my group to see it also, the ability to drop a live waypoint while flying, to help direct others in my group to see it would be a great tool as we showcase the game and graphics.