Didley and Roger
The RNAV's existed alright, Forkie and I say here in my lounge with the current at the time chart discussing what options may have been at hand, and that was the one. Runway aligned, lower and heck, sooner or later there was descent below a minima, surely its better to fly a predetermined glide slop, the FO monitoring the GS all the way, double checked with the RAD ALT, and make it into a dodgy ILS/LOC approach. Carefully planned and executed, albeit not exactly legal, they may have all needed a change of undies, but in one piece.
Just my thoughts, not enough outside the box thinking. Perhaps they did not have the endo so did not carry them
Of course the company and the regulator led them there. But when your back is against the wall is ditching your only option?