[Piotrsko]

Just replace the heat /cooling head unit, use existing ducting. Your method is kinda pricey for being more efficient on a room by room basis. Wont make much difference heating/cooling whole house on an return or start up, but once at temp, the room control is nice.

You could get the same effect with controlled dampers at much cheaper cost. Mine throttles up or down based on required temperature input and what historical data that it stored says should happen inside the house. If the difference between house and outside is only a degree or so, you never hear the outside coil fan run