There'll be a new model of power armour, the T-77x that was developed and deployed just 2 weeks before the great war began. It'll look like a slightly redesigned T-60.
Since the main stuff has already been covered in this thread...
More FO1 and 2 weapons. I want my 14mm pistol, deagle and FAL to be in the base game for once.
More interesting tribes. Maybe a chance to get to know the 80s from Honest Hearts.
Cities that do not have massive piles of rubble...
I reckon when that's released the FO4 modding scene will improve quest wise. There might be a Project Nevada/FO3 wanderer's edition style overhaul which makes the game more playable using the system. Besides, the inbuilt limitations haven't stopped anyone from making quest mods.
The weapon...
NCR troopers only have one firearm on them at one time, according to the GECK leveled lists. This varies on the trooper's post in the game, with camp Forlorn Hope troopers having caravan shotguns and other low tier guns, regular troops have service rifles and troopers in the battle of Hoover Dam...
With regards to the water tower in Goodsprings cemetery, you cannot actually drink from it. There's no water valve that you can use, suggesting that it is not in use. Also, the people of Goodsprings get their water from Goodsprings source, and the latter part of the tutorial quest involves...