Beyond what I could read so far,
it seems something interesting, I did the research on the forum and not to much about it.
What is the opinion of the "ingeener"
Foveon is a very religious subject. You have people who own a Sigma that uses it, and think that its god's gift to photography, people who used to use it but don't anymore, people who would like to use it but don't want to invest in a proprietary lens/accessory system, people who think the images look defective, etc, etc.
The issues are compounded by the fact that the Sigma cameras that use the Foveon sensors have not only a different type of sensor than most digitals, but they also omit the anti-alias filter, which prevents a camera from recording distorted high-resolution detail that isn't accurate to the subject, but the output *looks* sharp.
They do resolve three bands of color at each pixel, unlike most digitals, but the discrimination between those color bands are much poorer than the results with the colored filter arrays used in most digitals. The blue channel doesn't distinguish well from green in the overlapping ranges, and the blue channel is not very well saturated; IOW, the blue channel is very close to being a panchromatic grey channel, with a slight bias towards blue. The result is lots of chromatic noise in some cases, and large blotches of off-color in the deep shadows.