Which type of NDA are we talking about here?
The NDA is just that.....Non-Precision.
Legally, (at least in the USA), you can descend to the MDA at the FAP and fly the final approach at that altitude. That method is generally frowned upon by most.....whereas the descend expeditiously so as to arrive at MDA slightly before the MAPT.
We have to discuss what determines the MAP.....a Beacon or Time....before we can adequately discuss the methodology of using a Vertical Descent Criteria, in my view.
If using an approach where the MAPT is a Beacon then Vertical Guidance might well be appropriate. If the Beacon is behind you.....and Time is the determining factor....we would have to rethink what we are trying to achieve.
I prefer to get down to the MDA and fly at MDA to the Missed Approach Point....with the goal of getting visual in time to locate the point of landing, hopefully do so in a position to land straight in....or nearly straight in without having to circle to land. Remembering Circling to Land requires a higher MDA.
A NPA does not mean you will be aligned to the Runway in use.....and also does not mean the Airport will be in front of you.
Now that we have GPS.....knowing our position and track is much more precise even if limited to NPA use.
Which also begs the question.....are we talking about a GPS Overlay or GPS NPA?
Could we be a bit more precise about our Non-Precision?