I find it all pretty funny as I do not give a rats A$$ what my guns look like , if they are cool looking , and all that BS, I care how they function that is priority number 1 with me yep I bought a DPMS off the rack and I changed the handgaurd, trigger, and muzzle brake /flashhider.. so lets look at those changes... handgaurd on original was a brick and felt like crap.. i chose a lighter apex , trigger i chose thanks to 98 was the giesslle ssa-e, and the muzzle brake is a AAC all my guns have them so all my supressors will fit on all my guns... the upper and lower is fine as is the barrel it will shoot better than I can shoot it the slideing stock is fine it works great, and all the other little parts like dust covers and pins etc are all fine i would have saved nothing building from scratch... because I paid for the whole gun what a upper and lower set and barrel would have cost me for x brand...
I agree with the guy if you want to build some super cool rifle then do it from scrath but in the end function is all that really matters... IMO.