Good design, with many parts I'd install on a plain AR15.
Still, I have two questions:
1- why not a folding stock? If you're going with a 16" barrel, and a piston gas system, why not take advantage of it and install a folder? (unless it still uses the butt recoil spring and can't)
2- why a 1:9 barrel? Since bullet use seems to be evolving to heavier weights, why not a 1:7 barrel?