Interesting AND VERY GOOD thread/topic!
Anything about building a custom rifle is a good thing!
Iffn I've missed details already mentioned, please overlook my redundancy!
As for the barrel, go with a 1-10 twist. Handles anything in the .30/06 including pills lighter than 150 grains and heavy-weight bullets to 220.
Last week or so I was in Wally World and one store still had ADL 700's in .270W for @ $379 + T. However, I like the idea of owning non-registered pieces bought from second-hand private parties, so "used" wouldn't bother me and might even be preferred if the rifle was going to ber a "truck gun" or "walk-me-home" piece I didn't ever want confescated at a roadblock during a SHTF scenario.
Also, I've been toying with the idea of rebarreling a 700Ti to .338/06 if i bought that rifle in an '06 and not a .308. I want my rifle to easily kill elk and an '06 handles 180 / 200 grain bullets better than the shortie. I don't like Remington's wippy whimpy "mtn profile barrel" however.
Maybe I'd go ahead and rebarrel to a heavier custom tube in '06, but I'd go 1-in-10 and even a 24" length. I'd choose a contour just heavy enough to give me enough steel to guarentee accuracy. MOA sounds more than reasonable.
If I change the stock from a "Remy Titanium stock," it will be to a Basner stock.
I love the .308 and its versatility, but like the idea of shooting 180 and 200 grain elk bullets.

In the .308W I see little need to shoot 180's over 165's. But that's me.