Some thoughts:
I understand the desire for the AC specification, what do you like about the Apple Airport Express and why do you need it to have AC?
Now, if you own Apple Stuff, that has AC, why not get the Apple Airport Extreme?
http://www.apple.com/shop/product/ME918LL/A/airport-extreme?fnode=58
I think the design spec for the Apple Airport Express is targeted to a small and simple "WiFi" adaptor/server for a small and simple wireless network. AC is outside the scope of the designed cost and capabilities.
Still, the Apple Airport Express makes a great Airplay endpoint, wired or wireless, connecting to an audio system via analog or digital cables. Maybe hat's a feature the Apple Airport Extreme and Time Capsule should have in the future?