Will go on testing it.
Also, the new FS layer still has some conflicts with SdFat library, so I had to comment every SdFat code in my Sketch_Buffer.
This https://github.com/esp8266/Arduino/commit/59a9f857866965f9b73fde7f0a5edd0b40a318eb (Resolve naming conflicts between FS and SD library ) was not the solution for your prob?
ESP8266 Arduino add-on
Arduino IDE 1.6.5