I have a gateway with the ESP8266 according the MySensors example. I was bothered that I don't have enough IO pins to connect the standard leds and the inclusion mode button. Therefore I used a PCF8574 I2C bus IO expander, so I have 8 additional pins available to connect leds or buttons. Instead of the MY_DEFAULT_XXX_LED_PIN defines I used the MY_INDICATION_HANDLER option and connected it to the PCF8574 I2C bus IO expander.
Unfortunately this does not work for the pins of the inclusion mode. Therefore I added the option MY_INCLUSION_INDICATION_HANDLER for a custom handler in the MySensorsLibrary. For this I made the pull request #1483.
To demonstrate the usage I provided an Example Project . I added it as an extension to MySensorsArduinoExamples and it is located in the dev_maxwa_InclusionExample branch under the MyWemosGatewayWire example folder.
I would be happy if the example is interesting and useful.