Omg, make world exploration/interaction as your primary focus. It's a crime not to use such beautiful world as a primary component of your game.

Need some quest system to guide the player when they feel nothing to do. I havn't figure out what the endgame will be.

No need for this. Basically something like crafting -> exploration -> crafting loop might work. That means that some components may be acquired only in some specific places, then those can be used to craft items which allow for even more exploration and access to more exotic places and ability to interact with world with bigger variety of ways. Of course, someday this loop might end, but it will be nice adventure. Endgame might be simple "see all biomes" quest or something like that.

You might want to check this game named "King Arthurs Gold" where you basically have a side view 2D grid of ground/stone/ore/tree/whatever,

Nice, I just checked the game. Some mechanics of it definitely worth learning. Although, making them work in 3D is really challenging considering the time and manpower I have.

I'd make a "Seige Defense" game. Your objective is to defend a town, person (king), or holy relic from invaders.

Yes, thanks for your ideas. I was actually working on a design similar like that, and found the hard part is to make the AI work in this dynamic environment, and not sure about if putting all the effort in it will result in "equivalent fun" to the players. Perhaps more effort in the PVP mechanics will bring more fun in this type of game.

Omg, make world exploration/interaction as your primary focus. It's a crime not to use such beautiful world as a primary component of your game.

Thanks, I'll review my thoughts about giving that up, and put some more research time on making the world big and rich enough and see how it goes.

FYI, I am in Canada and it denies my access to your video.