In my opinion this theme a little exposed.
Although it is very interesting.
For example, the Fallout in the world, due to the lack of heavy equipment and heavy weapons, the role of fortification.
For this reason, fighting trench will have a character as during the WWI.
With a score to settle with the NCR, the Brotherhood of Steel and the Enclave former soldiers should be hidden to help the Legion of Caesar.
Therefore, in the Legion of Caesar must be evocatus - soldiers of the Brotherhood of Steel and the Enclave avenging NCR.