To be honest there isn't really a lightweight large frame AR. The best possible option would be a light weight 20-22" barrel 6.5 CM or 6XC. Even a light one would probably turn out at 10.5-11 lbs with optics however.
If you forego true 1000 yd capability, an AR-15 in 6.5 Grendel or one of its 6 mm variants (6 mm AR, 6 Fat Rat, etc) would much lighter, handier, and with lower recoil.
Agreed. I'd recommend Alexander Arms. They did share in the development. If you want 1000y and a small frame, time to contact Robert Whitely with 6mmAR. It's Grendel necked down. I'm sure I'll be flamed for this, however, here goes. My 22lr will go 1.5 miles, but accurately? My Grendel will go 1000y, but within 1MOA? I'd prefer a better balance of high BC and velocity, which I think you get from 6mmAR. I love my Grendel, and I feel it's best for sub 800y, specifically with 123gr bullets, but I'm also biased, I've a 6.5 creedmoor AR for 1000y, or a 6.5x55 swede for long seated bolt action fun. That said, wind is really the issue, I think the Grendel is still supersonic at 1k.
Cost? I'm using formed 7.62x39 brass for plinking use, or Lapua for matches, can't argue there. 85-100gr bullets aren't too pricey, but it isn't a 223 with low cost bullets. I never did bother with sub 130gr in my creedmoor, so the Grendel fits in nicely there.
AR-15 build will need a barrel/bolt, and get a rebuild kit and an extra Grendel extractor to cya; and magazines are diff too (follower). I just built mine in a spare upper and caliber changes are fast and easy; magazine swap and two pins.
Hunting: I'd take a 6.5 Grendel after whitetail before the 6mmAR, both would be for under 200y use, and a good partition will perform well in both. Just my opinions there.
-Mac