You have to access the Official Folder, and look for the Generic folders. Open their aircraft.cfg and look for IsAirTraffic=1 and change it to 0. You have to do this for ALL of the Generic Aircraft folders.
Then if you find ICAO_Generic=1, also change this to 0.
Then you have to open the Asobo A320 folder, and look for the Aircraft.cfg as well. Then Add ICAO_Generic=1 in there at the same position as the one from the Generic aircraft.
Once you do this, it will force the sim to use the Asobo A320 model as your generic Air Traffic model, regardless of the actual Live Traffic aircraft type. And if you have a matching A320 livery with a matching ICAO Airline code that is also set to use IsAirTraffic=1, it will use that livery.