In real life, all airlines depart via a specific waypoint or route.
For example: At YMML (Melbourne) Departure RWY 16:
Track to Waypoint HORSH; Turn Right.
Track to Waypoint ALBAK; Turn Right.
Track 316° to Waypoint KEPPA; be cleared Departure following FPL or to specific airport.
When departing, request a specific waypoint you will be departing to / from.
Pilot Emirates 408, requesting takeoff, RWY16, Departure via HORSH.
ATC Emirates 408, takeoff approved, RWY 16, Departure approved via HORSH.
ATC Emirates 408, await clearance before following FPL
Pilot Roger, Emirates 408.
ATC Emirates 408, clearance approved.
Pilot Roger, Thank You, Good Day.
It would go something like that. I’m no ATC expert so I might get something wrong in that case.
For IF, this feature would prove helpful with sequencing the planes that are departing not just arriving.
If a plane that was landing at an airport with 2 landing strips in the same direction (e.g 25L and 25R) was landing at 25L you wouldn’t want a plane departing towards that plane. On some occasions, the ATC will reject the request to depart via a waypoint due to the sequencing of arriving planes. So the ATC will have an option to depart via a waypoint in the airports vicinity / 10nm.
Again, this is for Expert server / IFATC only.