I personally think that adding more weapons is asking for it to become more of a shooter/fighter, and less of an rpg
that said here is my wishlist
1: realistic characters, the likeness of the characters of megaton and rivet city, i personally found the characters from new vegas to be less than believeable than the fallout 3 ones.
2: more detailed enviroments, or at least keep the detail level of fallout 3 in your areas
3: better DLC, as at least 2 of the dlcs of f3 werent quite fitting to the fallout style
4: Harsher wasteland, more along the lines of fallout 3 with wanderers edition
5: A meaningful storyline, not a story along the lines of a basic "pick a faction", make it important to the survival of the wastes, or the destruction of the wastes.
6: Don't focus on the BoS
7: more detailed enemy factions, the raiders in fallout 3 fell short of having a real reason to be raiders, which is one thing almost no game seems to put meaning to.
8: more unique areas, that really leave an impression of the struggle to survive that happens in fallout.
9: dont have living trees, just dont, it breaks the style.
10: have a finite limit on number of companions you can have at once, and have a more in depth quest to get them to be your companions. having too many companions makes the game much less enjoyable.