Regarding deep sleep & stuff, should work. Have done something similar, a simple "door sensor" that with a very small amount of hardware can do the reset needed for ESP after a deep sleep, so it is properly reacting in deep sleep on a "external interrupt" event. You need to play a bit with MQTT if using LWT but should work OK.
Available on Tindie: https://www.tindie.com/products/nEXT_EVO1/universal-ac-mains-dimmer-mpdmv41/