Items I wish to see in NV...please note, I have FO3 for PS3, and do not have the luxury of mods, please feel free to use any ideas in future mods.
1. Make the main character not from the vault since its not a sequel, start off in some place outside of Vegas, maybe some farm or something. Also making it so you can be a ghoul if you wish. Or maybe making it an unlock after beating the main quest first, and have higher resistance to radiation, and people start off hating you, but gives you access to places where only ghouls can go. Also, maybe not actually doing the main quests, perhaps it is someone else, or a group that is doing it, and you just happen to come across
2. It would be cool to use Caps and Chips as currency. Perhaps when you reach the entrance of Vegas, you can exchange them, maybe 2 caps for 1 chip. Make the chips universal for all casinos if there are more than one. Even if there are different families running them. Maybe make this a quest to calm down the heat between them.
3. Make gambling a big thing in the game, maybe even a skill like speech, also used not just in the city and casinos, but also lets say you come across a small settlement, and don't have any caps to pay for a bed, perhaps ask the inn keeper if he'd like to play some cards for a bit for a room. Also adding on this, it would be very cool that side quest would be that you had to compete in a card tournament, and since World series of poker is popular, I've already thought of the name for the game. Texas Hold'em = Wasteland Hold'em. Similar rules, and such, but make the quest that you have to get within the top 3 spots, and win a nice amount of caps/chips, maybe a trophy or something to put in a home, as well as people knowing that you won throughout the wasteland. Slot machines as well as blackjack would be good to have as well to have as well.
4. More settlements/outposts/towns/bases, FO3 was lacking with any places with life. Was just Megaton/Rivet City/Tenpenny. I saw a mod for FO3 where you build your own settlement, and fend it off from attacks and whatnot, little places would be nice where perhaps you can interact with and maybe ask for money or supplies, and you'll add their location to a caravan or something. Also they have quests for you as well which might have different karma outcomes. Would like to see more places where you can have residence in, through buying, quests, trading, killing, or maybe winning permanent hotel suite for winning said poker tournament.
5. Upgrades being able to be made to weapons as well more types of weapons. I know this goes against Fallout in general, but would be fun to add things to weapons, such as a scopes, extended clips/magazines, silencers and RIS fore grip for better accuracy. These upgrades would obviously only allowed for weapons it makes sense for, i.e. no scoped knife. Upgrading armor would be nice as well, maybe being able salvage from one type, and being able to combine it to another, with the old one's added effect, and make a hybrid piece, but limit how many can be on at a time, or add negative effects for good positive ones.
6. This one might be hard to do, but maybe be able to set a timezone your in, and the game would play in real time, so if you you play mostly at night, you would play in the moon light most of the time, making Night Person and Solar Powered Perks more viable. Or if that isn't as plausible maybe make days last longer, maybe 3-6 hours. Weather effects would be great as well, I know due to graphical/memory/Framerate issues arise, but they make the game come more to life, dust storms, irritated rain, perhaps acidic and regular. I liked some of the other ideas already in the thread about you get radiation from being in it too long, and maybe acid rain degrades the gear and weapons your wearing, as well as taking light damage unless you find cover till the storm passes. Fast travelling should calculate how long it would take to travel by foot, so if you quick travel how long it would take on foot, and progress to that date/time.
7. Vehicles, I know it might be hard to integrate this in the current game engine, but perhaps they could have quests which would involve you as a passenger on/in a vehicle. From cars, motorcycles, vertibirds. Any would be fun to experience.
8. Difficulty, would work well if instead of scaling, perhaps just making harder difficulties where items are more hard to come by, such as guns/ammo/meds/food. This would make players make choices such as sneaking instead of fighting.
9. Sometimes when I load my game, I always feel like I have to be exploring or doing a quest, would be nice if we could be able to do other things, such as opening up a store, filling the shelves with stuff you don't want, and if your barter is high, you can get some good caps. Or a store that repairs items for others, and you can hire someone to be there when you want to continue on. Other things to do in spare time perhaps fishing, making a still to make and sell alcohol. Books would also be a nice addition as in Oblivion where you could read history, as well as fiction stories.
10. Vats, I would say still keep this as part of the game, but make it so you aren't in god mode while in it.
I have more ideas, but out of time at the moment.
Sorry for the wall of text, please feel free to leave feed back. Thanks