Wi-Fi cannot turn on! Accidentally deleted /etc/wifi folder
Try harder to find firmware images for your phone. A factory reset might not work, as it only wipes data and cache partition. The etc folder is in /system/etc, /etc usually just is a link to /system/etc. Therefore you would need an image of the system partiton.
Well, if you can't find such firmware, it might not be a device thats common used, and therefore - if you are lucky - there was not a lot of money around for software adaptations from the manufacturor. Try to get firmware for similar devices, watch out for the same android version, and second on similar hardware / components. Download these images, unpack them and try to find the needed files.
Maybe you can just grab another device, from a friend or so, and look for the files. You might also consider having a look on aosp and taking the files from there. Watch out for the correct android version.