Architecture with two controllers

[mysensorsAlarm]

Goal: new alarm system for our house.
Requirements:

• Support of both wireless and wired sensors
• If the home automation controller fails (e.g. power surge), then the alarm system shall remain operational
  My Architecture idea/ proposal:
• ‘Controller interface 1’: only Alarm system logic on a micro controller for reliability (Arduino)
• ‘Controller interface 2’: only status reading (Homeassistant)
  Illustration of situation:
  

Question:

• Is the following architecture suitable for my main requirement? I do not understand how to e.g. combine the two, serial and Ethernet, controllers
• Can I combine the alarm system logic in the mysensors gateway?
• Other suggestions based on your experience?
• I’ve searched but was not able to find an example of a comparable situation, but if there exists one… 
  Thanks a lot in advance!
  Kind regards,
  Tom