I havent got much time, but if im in mood i can help out a little bit.
The stupid thing is that metin uses a shit Field of View and a stupid fog rendering.
This makes the sky looking terrible and because of the fov the user only views the ground.
It would be possible to make the object rendering better with shaders, because the textures are too bad.
I dont think it is the granny format, althought the oblivion invidual character modification would fit to metin2. But I dont know much about those things.
By the way, if someone has SPT grass, could you send me some of them? I could customize the lod for it so people dont get laggs, if there are too much meshes.