Though I hate Bethesda and wish it as a company caught a horrible disease and died (lol), it wouldn't take many steps for them to make FO3 relatively enjoyable.
1) Choice and consequence. In this aspect, at least from very limited previews, it seems to be an improvement from Oblivion. Or, at least you get to blow up a town. That's better than nothing. The ways it sounds, though, they'll probably end up going into good/evil/neutral paths. But hey, Bioware can get away with it too.
2) Hire writers.
3) Don't freaking dumb down combat. The combat in Oblivion was a major step up from Morrowind, yes, but that doesn't mean it wasn't bloody atrocious. Melee in Dark Messiah (demo) is fun, melee in Oblivion isn't. With a (potential) emphasis on ranged weapons, they could get away with a decent FPS combat mechanic, but they could still screw it up. Shooting in Bloodlines wasn't particularly compelling. But that's what happens when you try to mix twitch and stats. An awkward compromise. This could be hit or miss.
4) Groin shots.
5) Fire Todd Howard.
6) Take pictures of all the $$$ they'll make and send it to Hades and Gabs.
7) Help finance Interplay's FO MMO.
Make subtle references for FOPOS fans.
9) Catch a horrible disease and die ROFLTUNASANDWICH
10) Kill Role-Player.
The list goes on, but hey, it's a start.