Did you look closely at the previous post's system for attrition? Did you plug in some numbers to test it out? Did you find out where the system works and fails? Did you notice how incomplete it is?
The post only details hot weather effects on attrition, what about cold weather? The heat index is only valid for temperatures above 80F and humidity above 40%, if you try to use the charts' equation for cold weather, you get nonsensical results.
What type of data we we plug in? High temperature, low temperature, average temperature? Desert travel can be brutally hot during the day and freezing cold at night, how does the above system take that into account?
So there's the direction for the next post, finding what the system is incomplete and making it more robust. Always push your design, always test the fringe cases, and always strive to make them better.