EDIT3: Seems that I solved it, but needed to turn back to Lollipop for using the CDS information from the MTK EngineerMode (since CDS is not available in Marshmallow)
+ I saw that Wiko deleted some things to the MM firm, putting it to a challenge to reinject the IMEI. For example, in the V18 (Lollipop: First Version), the apedata was present, which is not the case anymore in the Marshmallow one. The EM Simlock and the CDS Information from the MTK EngineerMode (present/available in V18), has been deleted too, making it impossible to repair the IMEI. As people said the "Chamelephon" app could recover it, I tested it and it didn't work. So the only changes you can do are only in V18.
++ Wiko did put 6 VERSIONS of the NVRAM, changed the 5MB original NVRAM dump to 11MB (as verified on TWRP Marshmallow and TWRP Lollipop (hanuma the saver !)), and deleted the essential apps for recovering IMEI. Now I managed to get it working, but now i have a freaking NVRAM WARNING = Err 0x10 on my WiFi.
plot twist: Try flashing the v31 using MTK SP Flash Tool, and it will recognise as a Vietnamese phone (not jk, personal experience)