[werk_ag]

Firstly, it is quite complicated. 
Secondly, it is not possible to connect a CO2 sensor.

I agree!
By my experience during the last year, I believe that the best results from the AQM sensor comes when it is well exposed to outside air, but not directly exposed to the weather elements, specially the wind (this is specially important for the CO2 sensor).

Perhaps a simple box, with some ventilation orifices may be enough.
Mine only have ventilation orifices on the bottom side.
We should not be particularly concerned in get good outdoor temperature readings from the T/H sensor used on the AQM. The main purpose of that sensor is give %RH readings, from as close to the dust sensor as possible because these readings are used in PM2.5 calculations (compensation %RH).