I think it's funny how so many guys think they need to "upgrade" the lower to get rid of the polymer. How many people have ever had problems with it? There was one batch of lowers made with a bad batch of polymer and they were replaced by Armalite and other than that the only guys that had problems were the dummies that released the upper and let it swing down and slam into the lower breaking off the tabs. Treat them right and you'll never have problems.
As for all the guys that don't like the stamped upper, keep in mind that some very good quality rifles are built with a stamped upper and I don't hear owners whining about it, ever hear of the Swiss Arms family of rifles?
Listen to yourselves, I want a CNC aluminum upper and lower and I want it for less than the polymer lower and stamped upper models sold for. That's just plain stupid. You probably want a heavy contour match grade barrel and for it to shoot sub moa for the same price they sold for in the US 10 years ago as well don't you. All these upgrades you want cost money, if you get what you are asking for you're looking at a $2500-$3000 rifle and you may as well just buy one of the currently available black rifles.
The AR18/180 rifles were designed to be a cheap to produce reliable lightweight battle rifle and I think they did a great job. I still regret selling mine.