1. Definitely what was said above about changing the map more to your liking with the time of day and weather.
2. One thing that I have always hoped and dreamed of is being able to add a sound track to your map using some sort of transfer system where you can put in a soundtrack (or song) from your Xbox so that you can set even more of a mood for your maps. This would be a pivotal move in a whole new direction for for forge and it is realistic with the Xbox one. If anyone remembers the ominous maps in halo 4 that were similar to slender man and such other maps forged underwater just think of how even creepier it would be to have a soundtrack to just crank up the intensity, let those goosebumps raise higher, and let the screams be even louder.
3. Another thing would obviously be the budget but I won't go too into that.
4. Also, I miss how long the pre game lobbies were in halo 3 this gave people a chance to look at other players' file shares.
5. What would be amazing is more special FX. The ones we have are great, but it would be really cool to have one where you could make everything have a glowy type of look to it or even a shadowy look to it. I explained this terribly but hopefully someone gets what I'm trying to say haha.
6. And AI should be implemented to the online. If anyone played Gears of War then they know what I will be getting at here. It really sucks when people leave the game and you have to sit and suffer because others can't handle the heat. I think that an AI should spawn if a teammate leaves and des pawns when a player joins. Also a combat training type of private match would be great for new players and for testing weapons. It could be called the training ground.
7. It would be incredible if we had items despawn after a certain time. This is very similar how we are already able to have items spawn after a certain period of time into the map. BUT we have yet to have the ability to have items despawn after a time of our choosing. This could go hand in hand with progressive maps for infection/flood.
8. Item deterioration would be fantastic! This would be somewhat how it is in Battlefield 4 where buildings would be blown out and fall over (more of a dream than a reality). This could be only be on certain pieces like how it is in call of duty ghosts where there's a mark on certain walls where there is an opportunity to blow a hole in the wall.
I have a lot more but my fingers hurt.