According to devs world of Greedfall is inspired by Scotland, Iceland or Orkney and I hope they will use it for good effect (it would be fine to walk in some infamous moor etc). Few pictures:
Anyway I think that the location of big island gives opportunity for some fresh idea(s). So here is my suggestion:
1. Sea cliffs + Climbing + Caves on sea shores
Imagine cliffs on shores and below them, just between the sea and cliffs, is small zone of land that could be short or pretty long along the shore. Imagine there are places fo exploration like caves (including caves that are partially underwater) or small gorges or capes going into the sea. It would be nice to be able to explore these unique secluded places near the sea - maybe its not completely original, but I think its fresh experience and would use the location well and its doable.
To make it more interesting you can use one non-combat skill for that and that is climbing. You need to invest some point(s) in it and have rope. Climbing itself will be just simple short animation and then your hero will stand below. Some places will be more risky (need more point in climbing), others pretty easy. If you have companion that is good climber he/she could boost your skill.
Climbing was done in RPGs few times, but usually just to get higher. Now you could use it for exploration of unique sea shores.
2. Caves that are flooded in floodtide
Some caves on shores can be explorable only in certain time when its low tide. And you shouldnt waste too much time inside. Becase when its floodtide water will rise and flood whole cave (and could eventually kill you).
Its probably too tricky to do with your budget so I dont expect anything like that. But its not bad idea if you think about something fresh for exploration. It would be great if you could make something close to idea 1 + climbing skill, at least partially.