Okay so, maxing out guns, taking shotgun surgeon and and stay back... fairly obvious. But what other perks should I take?

Cowboy Perk could be useful if using a lever action shotgun

Rapid Reload MIGHT be an option or better Quick Draw, since Shotguns usually have small magazines. Are you going to utilize VATS a lot?

And do you enjoy creating new characters a lot? Or are you still looking for the build that suits you the most? I can only recommend not exploit leveling and going with one idea further if you think it has potential. But that's just my way.