I appreciate the KISS principle behind your design: my point is that you dropped the statistical benefit of multiple V-refs for no compelling reason. The most accurate reference is at the top of the chain. You divide this down with fixed resistors and there is no increase in battery loading. The division accuracy would benefit from combining resistors. When I make mine I will see if combinations of values will give a close 10:1 ratio.
You were able to select a) V-refs and b) resistors, to bystep the statistical approach. I may not be so fortunate, that's why I will go back to (your) first principles
I will also add fine adjustment with a pot at the 12.5V point so that /all ranges can be set precisely with the one preset when I am next passing an obliging Calibration House.