I think standardizing the signal names, nomenclatures and colors for signals is a good idea provided that the application variations are taken into account such as in heat pump system Y signal in combination with O or B is used for both heating and cooling. The idea behind standardizing HVAC outputs on one connector (DB-25), as I understand it, is to make replacing one PCT with another one easier for the user, however, what is not been addressed is how much difficult it would be to terminate and route those signals in the field. There has to be a mating connector header/receptacle on the wall that PCT will have to connect. In the case of a system upgrade or a change, the number of wires may change, which will require the connector on the wall to be rewired. This will be a lot more difficult than the existing system, which uses plain wires that connect to terminal blocks on the thermostat. In my opinion, there are a lot of variations in HVAC applications, therefore, terminal block serves very well to accommodate all of these variations and makes the field installation and wiring easy.