Or something else that hasn't been tried: set the ecm up so that it can get feedback directly from a dyno like the dynojet power commander piggyback boxes do. So if the ecm can get feedback directly from the dyno then a program can be developed to automatically tune for power. Its pretty wild the stuff the dynojet program can do, even individually mapped cylinders. Its a wide open field for who ever can step up to the plate and bring the diesel world in line with the gasser world.
That's kind of where the a/f ratio comes in. Sure we can look at the tailpipe, but that leaves us with only qualitative not quantitative data.