I would like to see some differences between day and night (besides the certain kind of pokemon that appear).
-They should keep the day/night music differences:
If they brought that onto the 5th generation from the 4th generation, it will feel like something really mysterious is happening at night. And hearing the differences between the day/night music made the games more enjoyable, espically the pokemon center music. At least I didnt have to hear the same poke center theme everytime I went inside, glad they changed that up. I dont know why they didnt do that in HG/SS. I hope they bring it back in Pokemon Black and White.
-Certain trainers should appear at night:
Hopefully we can get some more trainer classes. It would make sense for some hard-core bikers to only appear at night. Hehe maybe some bikers with a Zouroak print on the back of their jacket lol. Maybe some supa nerds should only appear at night, maybe some expierments with their robo pikachus. Oh and Burgalers! I cant remember if they had that trainer class in DPPt, but they sure had them in HG/SS. That'd be fun to see them pop up at night around big cities (like the one we saw in the first gameplay of Black and White). You know what would be cool, if there is a dark gym (hopefully) that you can only fight in the nightime. It would just be interesting to see that :D
-Certain areas you can reach at night:
Its time to get creative with the cities again! They should have a town, or a city that hidden by shadows. Im thinking something like a village hidden in the forest (no naruto pun intented :P). Seriously, the city/village is only visible on the map (noticed I said map) at nightime, and you can access this area (only on the 1st visit) at night, and after your 1st visit, you can access that area anytime of the day. I cant think of how FLY can affect that feature, maybe you can just fly their at night lol.
-Certain berry trees/flowers should bloom at night:
There are some flowers that only bloom at night, so why not in a pokemon game?
-The moon?:
Since we're not getting a birds eye view anymore, I think it is time to introduce the moon into the pokemon world. I want to see the moonlights reflection in the water. Maybe some pokemon should evolve only when theres a full moon (or other moons: cresent, half, etc.) Now that would be cool. Maybe Zouroak can evolve in a full red moon, seeing how its eyes glow red.
thats all I can think of at the moment :]