Have you seen http://phalconphp.com? The basic idea of a framework as an extensions is pretty nice.
I must admit I have no idea of the work involved in the process (or any limitations), but if someone in the Yii community with C-skills has gotten inspired by phalcon, they might get the idea of porting Yii to C?
How awesome would a drop-in-replacement written in C be?
I think its a shame they decided to roll their own framework at phalcon. They should have sticked just to the basic concept of putting a framework into C-code by using something as Yii - and have others worry about architecture.
A working group of C people should focus entirely on keeping up with the PHP version.
What do you think?