Re: AI AW 338 lap mag
Depending on the barrel length, you're looking at a 17-20 lbs rifle, so decide yourself if that is what you want to be doing position shooting with. I can be done, yes, but not the most ideal. Also take a look at the need for the performance of a 338LM versus a .260 or .243. Hunting very big game at long distances is one thing, but taking anything in the lower 48 out to 800yds is realistic with a much smaller and more practical round.
Recoil is easy enough to control with the proper muzzle devices, so I wouldn't concern myself too much there.
I understand you have a deal opportunity in front of you, but if you aren't going to be playing the ELR game, I would seriously consider if it is too much gun for what your intended purposes are.