Hello and welcome to the club 
Feel free to introduce yourself here
I would advise for your SMS gateway to support MQTT messages over WiFi. Through MQTT you will be able to read and write all values/settings from all 10 HestiaPi individually (Read state at zone number 3) or globally (set heating off on all Zones ). Same applies for the multiple temperature sensors. For the multiple relays, you can use spare Raspberry GPIO pins and drive the 10 relays with these.
Sounds like a great project and I am very confident HestiaPi can support this setup but will require a lot of your time and configuration. Keep us updated