Regarding the eternal "should the stat be set to FAN=AUTO, or FAN=ON", a 2-way choice.
In a humid climate advice is to always use AUTO, because in a 5-minute period after a cooling call ends, the coil is wet and fan action would evaporate that water back into indoor air. Right? Yet some times people wish to use "FAN ON" for a variety of reasons. The 2-way choice forces a compromise.
If there were a 3rd choice, where the stat guaranteed the fan off for that 5 minutes, and only THEN would obey the "ON" command or setting... that would appear to deliver the benefits of "FAN ON" combined with the humidity control of "FAN AUTO".
Should be easy to design if there is a microprocessor controlling the functions. I submit that the 2-way choice is a throwback to mechanical controls, and we might adjust our thinking toward the future.
Thank you for reading -- Pstu