Ray,
Are most of your customers commerical? In a residential setting I don’t think I have seen more then 4 zones and that’s why esp32 is appealing. I get frustrated because it should be simple to have a generic version for esp8266 12e dev board for example which has more than 4 available gpios for relays or esp32 wroom dev board which has 8+. Both great options for a simple retrofit. Open garage is awesome in that respect.