15 Multisensor Arduino boards for temperature, umidity and co2 + display and proximity sensor

I need 15 arduino small boards to mount inside wall box. The project max size should be 80x40x35mm, of few mm more on one size. There is some work to create the pcb to connect all the sensors below On each one I need to have rs485 screw holes to connect the rs485 cable and share the read values via modbus. The sensors on board should be Sensirion sht31 to provide temperature and umidity (with good thermal isolation from other board compnents), a co2 mh-z19 sensor and a small pir or other proximity sensors to detect movements and power up the display. These should be on the right part of the board near the cover of the box, where I'll do some holes for aeration. On the left part I would have a 1.8" color display to show read values, a couple of calculated values, some I get via modbus, date and hour. On 3 of this sensors I would put a voc sensor too like figaro tgs8100. All the components should be low consume to produce few heat. I need you provide hardware and software source code. I need a prototype first and then we'll go on with the other sensors