Keep the 308, add 2" of barrel and loose the 175 SMK.
Keep the .308... loose the Win... add the WSM... add 2" of barrel... loose the 175 SMK (BC .49)... add a 195 gr monometal, BC of .66 @ an MV of 3200 fps. It will reach 1500 yds with a vel of 1400 fps and KE of 850 and it would stay supersonic out to 2K.
No offense, but in all seriousness, what the 308 Win can do, the WSM can do better.
Now, if we look at Brian Litz' article... "What's wrong with the 30 cal?", there is a strong argument for going with a smaller cal, like the 7mm.
IMO, a high BC 7mm monometal bullet, with driving bands for increased velocity and longer barrel life, delivered from a WSM, Dakota or RUM would be a great sniper round.
I think the best candidates are...
300 WSM
300 Dakota
300 RUM
7mm WSM
7mm Dakota
7mm RUM
Each has it's advantages and disadvantages, so the requirements need to be well defined to find the one that best fits the bill. I lean to the WSM's which would be more mobile, with longer barrel life.
I left out the 338's, for two reasons...
Excessive recoil and weight of ammo. The 300 and 7mm RUM would stretch these limits also, but IMO not overly. The 338's could however be used in special circumstances when needed.
-MR