Crazy or good idea?

[theholycow]

I had a thought this morning about modern fuel injection systems: What about one O2 sensor per cylinder?

Currently V-engines use one O2 sensor per bank (not counting the post-cat sensors) to make sure each bank gets its mixture controlled separately from the other, in case there's any difference. Well, then it's still averaging the cylinders in that bank...why not sense each cylinder and avoid treating them all the same? There's already one injector per cylinder, so it's just a matter of pairing O2 sensors to the injectors, monitoring individual sensors, and controlling their paired injectors.

They'd have to be right at the top of the exhaust manifold, obviously. They couldn't reasonably be wideband; I can't imagine that any amount of fuel economy or longevity from adjusting individual cylinders' fuel injection would ever pay back that kind of investment. Would individual narrowband sensors be better than single wideband sensors (common in the past few years)? Could they compliment each other?