It is certianly worth doing.

It's worth noting that the reason all cars have closed loop since 92 is due to the requitrement of a catalyst. Mixitures other than lambda 1 dramatically reduce the life of the cat. The narrowband sensor is also desgned in such a way that it can only really control mixtures down at lambda 1. A wideband sensor is far more accurate at othe mixture levels.

If you are going closed loop, and you wish to accurately monitor the fuelling, then an innovate wideband sensor and controller can be used - you don't need another narrow band sensor, as the innovate controller can ouput a narrow band signal to the ECU.