I'm interested as well - family members have been looking for a while, and they keep finding products that I deem as... low-quality, for one reason or another, and my requirements are basically aligned with what you are building.
Please let me know when your solution goes live :D
Similar product, different experience: I tried their doorbell and found it to be way underpowered once I turned on ONVIF. Huge, expanding lag between real world and camera feed. 20fps max is very oof too, even if you are going to use their protocol and software. And it doesn't work with physical chime boxes, so you have to use their plug-in chime or botch a converter together yourself.
Was really excited (trying to replace a nest doorbell) and then so, so disappointed once I got it. Their other cams might be fine but oof, the experience put me off.