I doubt that Forstchen meant for the aliens in Action Stations to be the Nephilim since Prophecy was not even realesed when he wrote it.Likewise,If Origin had made more Wing games,I doubt that that is where they would make the Nephilim originate from.Plus,those aliens were basicaly coming system by system and not suddenly through wormholes.To me, I do not see any logical or fictional evidence to support that theory.Of course everyone can have there own opinion.
The Nephilim could have come from our galaxy and very well may have. This is just a personal opinion,but I feel that the designers wanted something a little bit more interesting then just making them another alien race with another normal homeworld.This would fit in with Vearrier's ideas as well.And,interestingly enough,the Prophecy poster ad shows Nephilim ships closing in on our Galaxy.Of course, it is just an ad which means it should not be taken to seriously, but it is, I think ,a bit of info that might be worthy of mention.