Good argument...... but lets go back in time.... The Armed Forces Pay Review Body who recommends any pay adjustments takes into account a number of issues before completing their report and recomendations.
The X Factor takes account of:
It's a none contributory scheme = a minus factor.
RPI was used as the indicator = a minus factor.
Therefore the X Factor added was around 3.5% (not sure how that is used within the recommendation) so your pay rises were reduced in the past because of indexing to RPI and now your losing out.
CPI does not take account of the cost of housing - Mortgage, rent, house insurance, council tax, maintenance etc.... many ex service personnel don't get on the housing market until they are retired at 40.
Read the blog on the petition website many examples.........
(It's great being retired never had time for all this S**T before)