With the new design of the MBPs the 13" MBA is very close to the 13" MBP, and having just an 11" MBA, especially when it's 16:9 isn't a great machine. Making it 12" would seem to be a much better fit wit the 13" and 15" MBPs.
Defective components don't fall under the standard warranty. We've seen with automobiles that they've had recalls long after the standard 3 year warranty was over. I'm not just talking about safety issues but other things like defective paint jobs.