Method for Nextbook Ares 8 (solved)
I finally figured out how to change the MAC on my rooted Nextbook Ares 8, NXA8QC116.
There's a text file, max.txt, in /config/wifi, which contains the MAC address.
Changing this value, and then enabling the wifi adapter results in a new MAC address. This survives a reboot.
The standard methods DON'T work on this device:
busybox ifconfig wlan0 hw ether fa:8e:f0:f2:14:27
busybox ip link set wlan0 fa:8e:f0:f2:14:27