However, unity's terrian system still has many restriction, it's very hard create landscape in unity.
Why not update the terrain system? Now unity' rendering ability is powerful, developers now already can make awesome-looking graphic, I thought Unity Official should give a chance for artist developers, bring Terrain System to a new level, then, artists could use their ability to create big environment landscape as in Unreal Engine or Cryengine.
And, this is a ideal popular terrain editor for refering:
Mount & Blade 2: Bannerlord Games Engine-Video