So I had an idea a while back. What if there was a game where instead of playing the RPG, you created the world for it?
You could place areas, which are each rectangles of say, 25x25 tiles. An area has certain properties. Foremost in this is the spawn list. Adding monsters to the spawn list will make it so the player has something to fight. If you have no monsters, this is a peaceful area. You would start with a peaceful area, and then could click in any direction to add in a new area there. This is 3D, so you can also make areas above and below the current area. Each area has to touch another in some way though.
Placing tiles is pretty simple. At the top you have a selection area where you can select any tile you want, perhaps a dropdown for selecting different environments so it doesn't get too cramped. Then you simply click on a tile in the area to switch it to the selected tile. Tiles can be purely visual, can be solid to block player's movement, can be stairs to go up or down, etc.
There is a special menu for NPCs. You can place them on a tile, then click on them to give them certain features. For example, you can set them to be a quest giver, shop keeper, healer, etc. You can also give them whatever dialogue and appearance you like.
You can also place chests down, these you can fill with items.
Quests and Shops
You specially design quests and shops to give to NPCs. For quests, you first set up a name and a reward. Then you can add as many parts to it as you want. Each part could be "kill x monsters", "talk to y", etc. Shops, you simply add all the items that the shop will buy and sell and give them prices.
You have a certain amount of points which are used to place NPCs, monsters, chests, etc. You can also buy heroes with these points. Heroes will wander around trying to level up. They will complete your quests, buy from your shops, and fight your monsters. When they level up, you gain points. So your goal is to build things for your heroes. If you don't give them enough NPCs and safe areas, they will be killed. But if you don't give them enough enemies, they won't be able to level up.
I hope that makes sense. I'm not much good at explaining things.