Ok, I think you should do a open world RPG, like Skyrim or Oblivion in a way. Where we can go anywhere and explore ruins, caves, landmarks, abandoned mines, abandoned houses, haunted locations, forts, citys, dungeons, camps, swamps, forests, secrets, ect.
-We can make a few haunted.
-We can make a few underwater/ground
-We can make them themed to a location.
-We can make them scary or beautiful.
-We can make them colorful or dull.
-Ect...
I would like for your project to be unique, as if no one else has done the idea or at the very least did not prefect the idea.
1. A fair level system.
2. Better terrain. ( I never see any good landscapes ever from anyone.)
3. Adapting classes. This is my idea of the class itself builds to a player's gamestyle. Example they like stealth and hide and wait for the perfect moment to strike, their bows and arrows increase in damage and perhaps gain a ability to brew a potion that can be used as a poison to poison melee weapons and arrows. The more they use a certain item, the more benefits they gain from said item. (I already know this will take a while.)
4. If there is going to be magic involved, let me do the particle effects for them, although I'm not a scripter. I will have them made on the particle emitter and let you guys copy it into the scripts.
5. We should make all the quests different in a way. I personally love doing paranormal based quests like helping a ghost captin free from his ship or have a story behind the crew, like the crew killed the captin to steal the loot for themselves, but the treasure had a curse on it that only the captin himself could have removed, and the ship was lost and you must find clues in order to find said ship. Then you receive the valuables it once carried. I see this as a side mission.
6. I don't think any minigames should be involved, it does not seem to fit with RPGS.
7. We should all come up with new buildings and caves that are yet to be seen.
8. These are all just my suggestions, it's your map not mine.

I hope you like my point of view on this project.