Talking about psykers... a psyker could be a good protagonist for a Fallout game. Maybe some pre-war experiment, or maybe an experiment by some post-war mad scientist. Or someone just born like that.
Lots of ideas and themes to explore.
Fighting psyker-enemies of all sorts could be interesting.
Also could allow designers to have fun with gameplay. Remember VTM:B dialogues using mental powers?
Of course, it should also allow the player to ignore his power entirely and just get through with his normal abilities and a trusty gun.