Ok, I just realized.. you "Radiation Spike" suggestion actually sounds similar to a plot I was going to do once before. In which the timeframe is a decades after the Second War for the Hoover Dam(A.K.A New Vegas), three decades later to be exact, and at the starting point of the rp, it introduces a Player made faction(Mine, of course) which is a Church-like entity. The Slayers of the Faith. They are not evil, but they have grown to dislike mutants and Ghouls, but only for one soul reason.. over the last ten years Ghouls, Mutants, and Radiation have spiked in particular area. It has filled apart of the Mojave with more then irradiated animals and entities then a person can count. 

If you want, we can converse more on this concept, and I can bring over a lot of my ideas from my old, un-used plot.