Build a new WYZE monitoring home and integrate existing sensors already in?

Would you be able to start integrating existing door/window/motion sensors, sirens and other sensors already deployed in a house? Nobody wants to take out existing sensors especially when they are fitted unobtrusive.

If you mean to integrate with Wyze Home Monitoring, the answer is no. The new HMS won’t work with the earlier version of the Wyze sensors (V1) at least not as part of the HMS. You can use the new hub to connect them but they won’t trigger alarms. Third party sensors are completely out of the picture.