This is a good thought.
However, if something will block the airflow, ie dust or even a fan failure, this will be catastrophic.
The strange part is that bOS detects the sensors:
Mon Jul 29 15:17:37 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:37.036] AUTOMATIC fan control, target temperature 75 degrees (hot is 90 deg, dangerous is 95 deg)
Mon Jul 29 15:17:37 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:37.348] chain 5: found sensor TMP451 at chip_addr=f4, i2c_addr=98
Mon Jul 29 15:17:38 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:38.853] chain 6: found sensor TMP451 at chip_addr=f4, i2c_addr=98
Mon Jul 29 15:17:40 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:40.358] chain 7: found sensor TMP451 at chip_addr=f4, i2c_addr=98
Mon Jul 29 15:17:46 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:46.153] set_pic_voltage: chain 5: setting voltage 8.70V (PIC=125)
Mon Jul 29 15:17:47 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:47.311] set_pic_voltage: chain 6: setting voltage 8.90V (PIC=91)
Mon Jul 29 15:17:48 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:48.469] set_pic_voltage: chain 7: setting voltage 8.90V (PIC=91)
Mon Jul 29 15:17:48 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:48.588] Probing for an alive pool
Mon Jul 29 15:17:49 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:49.188] Pool 0 difficulty changed to 8192
Mon Jul 29 15:17:49 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:49.195] Pool 1 difficulty changed to 8192
Mon Jul 29 15:17:49 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:49.535] Rejected untracked stratum share from pool 0
Mon Jul 29 15:17:49 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:49.589] Network diff set to 9.01T
Mon Jul 29 15:17:53 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:53.758] sensors: 5/0 temperature read failed, using previous
Mon Jul 29 15:17:53 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:53.758] sensors: 5/0 temperature (0.0,0.0)
Mon Jul 29 15:17:54 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:54.424] sensors: 6/0 temperature read failed, using previous
Mon Jul 29 15:17:54 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:54.425] sensors: 6/0 temperature (0.0,0.0)
Mon Jul 29 15:17:54 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:54.590] API running in IP access mode on port 4028 (5)
Mon Jul 29 15:17:54 2019 daemon.info cgminer_monitor.lua[1531]: state sick because low hashrate
Mon Jul 29 15:17:54 2019 daemon.info cgminer_monitor.lua[1531]: /sys/class/leds/Red LED mode blink-slow
Mon Jul 29 15:17:54 2019 daemon.info cgminer_monitor.lua[1531]: /sys/class/leds/Green LED mode off
Mon Jul 29 15:17:55 2019 daemon.err cgminer[6644]: [2019-07-29 15:17:55.090] sensors: 7/0 temperature read failed, using previous
To bypass the error while trying to flash to factory, i used the SD recovery method.
This time the flash was successful to NAND and S9 boot to factory OS.
Then i installed the 201711171757 and all three boards were working again!
Seems that 201711171757 is really a saver.
I tested to flash to latest 2018 firmware 201812051512 with success and all boards properly worked. Including of temp sensors!