No need to oreplace anything if the Vista 20 system still works. I have a Vista 20 with a combination of wired and wireless sensors. I use an Envisalink board and the HE<>Envisalink integration. This allows me to control Vista20 states (armed stay, armed away, etc), detect Vista20 alarms, and use Vista20-connected sensors with HE. It has the added advantage that the Vista20 continues to function as a stand-alone panel so if HE goes south your fire protection does not.
https://www.eyezon.com/evl4.php
The integration is described here... you can run it either natively or on rPi. My installation runs natively as an app and device driver on HE.
