Personally I'd like to see some new areas but i'd like it to be like bloodmoon was with morrowind where it was just added to the map and you didnt have to do anything special to get there but swim or take a boat now i now that would be difficult with this game but atleast let me take my companions and maybe add a few more
BUt what i mostly want to see is like in morrowind you could become a vampire and with bloodmoon you could become a werewolf now i dont want those as options but i would like a way to turn yourself into a ghoul like if you got really irratiated like almost dead but not quite and then heal yourself and after a couple of days you go to sleep and you wake up a ghoul or something which would be cool since it would alter how people interact with you i would also like to see the ability to become a super mutant and or nightkin because then everyone would hate you except for other mutants and normal people could start to like you a little if you were really loved around jacobstown but then ncr and alot of other groups could still attack you on site and just make it really hard to get people to like you but you should still be abe to gamble in vegas
now i know these are big things to ask for but that would be amazing and add to the customization and replay value and i mean what i said with the super mutant thing would help balance it