Idea is nice, but I can see no applications for image processing on CHDK-programmed camera. If you'd have access to DSP part of DIGIC you could do almost anything related to the image procesing. CHDK curretly has no direct access to the DSP. Without that all calculations are very slow (for image processing).
However, GA could be used for such things as calculating good exposure, best threshold for motion detection or maybe even for object tracking (camera could control some kind of mechanic stand).
There are only two things that limit you - physics and ingenuity:)
You can't do anything that camera hardware can't. But if something is possible for the hardware the *only* problem is how to tell the hardware to do this.