The correct way to use any ESP8266 based boards with the current MySensors implementation is to configure them as WiFi Gateways with local sensors. You cannot make one ESP8266 an serial GW and expect all other ESPs to communicate via this one using the WiFi.
I other words all your ESPs will be Gateways but without any transport (NRF24L01 or RFM69 that is currently supported).
