Forget the PA system. The PA announcer was awful.
I didn't realize there was a big hullabaloo about the american flag not being in the stadium until I was reading a blog. I didn't even notice. Plus, since they had them all over the stadium grounds, I didn't see the gripe. Two days after reading the article, there was a blurb about flags being hung.
Jazzcat mentioned it, but I wanted to piggyback on what he said about the banners going up in the Cowboys HOF instead of the stadium. A compromise could be having banners in both the stadium and the HOF.
I think the reason there aren't more banners is it's more about the fan viewing experience.