Hello,
Few things comes to my mind.
You can call me sado-maso, but would that not be nice, to add radiation effect in to the Gun Runners workshop area ? There is toxic river around it anyway, so it just fits ! Putting some special suit with rad resistance (drives the economy) to do the job there, sounds like fun. And the feeling of tension is always welcomed, especially in such a nice location !
Also, I thought about changing weather conditions due to radiation. So, there might be the days when radiation appears in the different parts of the map. Players could check (or download) the daily weather prognosis via geiger counters (or pipboy). Being outside in such condition could cause certain effects. But this might be a nice diversity - even for PvP !
Maybe some unpredictable disasters or cataclysms could happen from time to time ?
Hope you like it,
Thanks