Having been in the front of a 727 when the nosewheel brakes came on, I don't think that it is fair to say that the system is "ineffective" ... terrifying, maybe, but not ineffective ...
I suspect that your comment regarding the AFM's not permitting a performance benefit is incorrect as there would be NO commercial sense to any operator's buying the mod .... I have some old 727 manuals somewhere .. if I get the chance I will dig out some numbers for you to illustrate the situation ...