I would definatly have the barrel nitraded, should increase barrel life considerably. I know you probably want to shoot heavy bullets out of it but man would a 100 grain NBT or ttsx at 4100-4150 fps blow the life out of deer!
I was looking at the 257 rum for about long enough to sneeze a few years ago, but as I had to trade my 7rum at 600 shots because of wear, I thought better of it and stayed away. The throuble is I'm wanting another 7 rum as a dedicated 140 grain bullet tosser. I need to work with 130-140 grain pills with my 7stw more before I play the rum game though.
If I were you I'd look at the 6.5 stw as it can be made from a rem or win in 264 without playing with the action; you only need to re-ream the chamber.