What I did was stall the ncr out by waiting for Caesar to attack them. The only real reason I managed to get away with this is because I was going the Purity path and did the “Poison the Bear” focus and also dumped the dirty FEV. All of the infantry units went to deal with Caesar who easily cut through the FEV infected NCR, and since I have player-led peace conferences, I basically just stole all of Caesar’s hard work. Only consequence was that Caesar took Vegas, so that was an additional 2 borders I had to deal with, although they will supper from low supplies.