Fallout 4 should totally pay tribute to Fallout 1 by being morally ambiguous as possible and do away with the Bethesda style good vs evil story. As for gameplay, Beth should learn from Obsidian when it comes to gunplay. Also keep gameplay options open as possible. For example if there is a locked door you can either lock pick the door, blow up the door, find the key, or talk a guy into opening it for you.