All of the barrels I've seen offered for the 22 Nosler are twisted 1/8, so that's not a problem, in fact one of Nosler's big selling points is that their factory ammo pushes a 77gr bullet at 2,950 fps from an 18" barrel.
The owner of the one 22 Nosler I've had a chance to shoot said that velocity was accurate from his 18" upper, a pretty decent step up from .223. Prior to shooting his, I was pretty skeptical of the round, but after sending several down to the 700yd berm and doing some reading, I now think it's probably one of the more sensible alternative AR rounds for some purposes, and definitely the most interesting of all the new Nosler branded rounds.
With 250 fps extra, the Nosler round is going to do better in the wind and carry more energy at all ranges than .223. I really think the Nosler would stand out in a DMR style AR Build, and when started collecting parts, I thought seriously about getting a 22 Nosler barrel. One of the nice features of the Nosler round over something like the 6.5 Grendel for this purpose, is that .224 bullets are usually quite a bit cheaper than even the lighter 123gr .264 bullets.
Nosler elected to use a rebated rim when they necked down the 6.8 SPC so you don't even have to buy another bolt, 6.8 mags are pretty cheap, plentiful and reliable. The only serious downside I see to the 22 Nosler is brass... For now, you can either shoot Nosler factory to get brass, or buy Nosler brass direct... At Nosler brass prices. Not Weatherby expensive, but also not cheap, especially compared to 5.56 range pickup. But performance costs, nothing is going to compare price wise to .223/5.56, but if the higher performance is worth it to you, the 22 Nosler might be a good option.
As an aside, what I really think would be interesting is if you could still get the LWRC Six8 receivers that were made a little larger to accommodate the special 6.8spc PMags designed for the Jordanian contact. Those PMags allow for 2.32 OAL, seems like enough that you could seat some of the even heavier, longer, slicker .224 bullets in the 22 Nosler case and get them up to useful velocities.