Yeh I put Daf Hewitt and Maule in the same boat at Ashley Smith tbh. They've simply never shown me that they have the potential to step up the one or two levels required to be a force at international level. I may be way off the mark, but being so close the the WC, now isn't the time to test them. Only uncapped players playing out of their skin should be considered like Faletau and possibly Tovey.
I completely disagree with your view of the warm-up matches. These games need to be used as a way to fine tune our game and settle on final combinations ready for the WC. They are not a time for experimenting with shoving wingers in at centre, and handing out first caps like candy. As I said, one or two uncapped players deserved to be tested, as they genuenly offer something that's missing from the current squad and are playing better than every other option. A little experimentation can take place in the Baabaa's match, but after that it's about selecting the best players and coming together as a team and sorting out the broken tactics.
Edit. I also just want to say that I'm not totally against trying Brew at centre. He has many attributes with could suit the position. He is however missing a cruicial element, and that is distribution. Distribution is very different from handling, and isn't just the ability to offload. Other Welsh centres suffer from this same weakness though, notably Jamie Roberts, so I won't be too harsh on Brew for that. If he get's some chances at centre for the Dragons next season, then Wales can consider it, but untill then he's not worth it. He deserves a shot on the wing though, no question.