Hi,
This is the sort of thing which management pilots come up with to justify their positions.
I think that Boeing/Airbus put a lot of effort into fuel saving/ efficiency and publish articles on it.
I would have thought that the FMC/FMGC would take care of calculating the best econ descent speed according to weight/ wind etc and the cost index.
If your company wishes to save fuel costs relative to other operating costs, could they not simply plan with a lower cost index?
This is what our company did, till we got in the way of everyone else, then they put it up a bit .