Why yes I've been designing weapons since I was a kid.
The features I listed were mostly foisted off on the Infantry by a clique of Target Shooters.
The 20" has proven to be overly long for actual need.
The Government profile barrel was a mutant compromise...the Target Shooters wanted an HBAR (ugh!), but the M-203 woudn't fit, so they left the outer part heavier and justified it by saying it was for the bayonet, last used in 1865.
The Target rear sight...has anyone fiddled with that in combat? Easy to accidently change your zero. Optics are the way to go, although the A1 sight worked very well.
The A2 buttstock is too long. Again another Target Shooter driven "improvement".
The pistol grip notch is just useless...I think it was added on to up the "new parts count" and justify the A2 to people who know nothing about guns.