Interesting, fo3 and oblivion both seemed pretty open for modding since there maps were already big with a lot of dead space to play with, unlike some current game maps being crunched together.
I did read that both of those games were harder to mod compared to say skyrim, since the community tools make it easier or something like that. It's been a real long time since I digged through info on modding so I could be a bit off.
