I'm guessing your CQC has an 18in. barrel? Just asking, I know it's the standard for them. But I've seen them w/ other barrels.
Food for thought.
-CQC would work if barrel is proper length, 18in.
-military's that still use the AUG in a DMR role use either 24 in barrels (Uruguay) or 20in barrels (Austrialia), as examples.
If I were doing a DMR type build, I'd want at least a 20in barrel for it. And though the factory optic 3x (which I have as my main HD AUG with Aimpoint on top), I'd want more magnification. At least 6x or something. But that's suggestive. Some countries have their DM's use 3x scopes, like ACOGs.
I've been pondering doing what you're doing. I'd already have it if I could find a spare, separate receiver. I've got a short flat rail. A 24in barrel, with Harris bipod, spare stock, parts, etc.
If I were you. I'd buy another AUG with a 20 in (or 24 in. if Pete Athens would swamp them out) :D barrel and an extended flat rail.
Uruguay. Not sure on the magnification they use. 24in barrels and this setup: http://steyrarms.com/accessories/aug/aug-bipod-flash-hider-kit.html
Australia. 20in barrel on their new EF88 (Atrax). Harris bipod, standard ADF 1-4x Elcan with an inline Kite 4x image intensifier.