If New Vegas sticks with VATS instead of, say, having a fully turn based system (cough)... I would definiately like to see VATS expanded a lot. Like instead of zooming in on the enemy, it goes into a sattelite view of the battlefield and you can do a lot more than just shoot. Like spend AP to move around with frozen enemies, make a choice between normal and targeted shots, use items, change your stance, choose between burst and single fire, and reload (It was SUCH a pain to not be able to reload your weapon manually in VATS) Also rebalance the damage modifiers and keep the enemies from moving around during VATS. There was nothing more aggrivating than having a 95% chance at your shots and not making any of them because the **** ducked behind a wall.
There is a modder at NMA who has been working on a huge megamod, and he's working on a lot of other interesting things like making enemies have a set amount of ammo to expend and action points. He also happened to do a pretty substantial rewrite of the AI so all of that working together means the bad guys no longer just charge at you and unload-- one of the absoloute biggest problems with Fo3's combat. In realtime it just looks ridiculous and stupid and plays cheap. I know in the short-ish turn around time for new vegas not a whole lot can be addressed about rewriting entire routines, but something needs to be done.