I have made a lot of models for Train Sim 2015 and they have some great shaders. One allows items to always face the player. This is particularly good for items such as trees where they are used as background and can be made from a single face with a texture with an alpha channel. Thousands of trees would amount to a very low frame pressure. Another is a good glass shader that gives a false horizon on the glass. Also a shader that allows certain named textures to show only at night which is great for lights in windows ETC. Perhaps these or similar shaders are already going into the engine but if not.......

Finally perhaps said before but real time day change would be great as found in Train Sim 2015 , Skyrim and many other games.