My take, would be to extrude it out and think of it in a way that you could make it into a modular system.
Why? Ease of use later on. Even if it takes a bit more to implement.
Think of a somewhat universal scenario and variables that you would require on a step by step basis.
So you have mission -> current step
Each step needs a goal.
completing all goals completes the mission.
If you want to go the step further I would let all of the settings for those missions be read off additional packed text or csv sheets. So you can later on create an editor or easily add missions…
The bigger issue you will have is defining the types of objectives.
getting from a to b
Talking to people
Doing this case by case is no doubt easier at first, but as your game develops it gets harder when you don’t have linear levels / objectives.
You end up needing a quest log and a quest system, which is exactly what I’m suggesting I suppose.