Hello,
I use both Homey Pro (at home) and Homey Bridge (at the summer cottage). I am aware that there is a good home security app for Homey Pro (Heimdall).
With Flow functions, the necessary functionality can of course also be made for Homey Bridge.
However, it would be really good if Homey Bridge also had official applications made/supported by Atom for key functions such as…
Fully cloud-based heating and security, what could possibly to wrong 
I don’t see much of a difference here that Homey Pro works at home (but can be controlled from outside the home > with an application). Then is possibly paired with the Google ecosystem. Or you have Homey Bridge, whose functions are practically 100% in the cloud. It is probably easier to break into a home implementation than a cloud service. Quite a lot of people don’t understand, have the know-how, or want to make the necessary security adjustments to the home network.
Consider the situation where your internet connection is gone. Homey Pro can at least continue running your flows and controlling your (fully-local) heating/security devices.
You are right about this. 
There is a connection via fibre in that particular property. Alarms from motion detectors etc. would of course not go through if the connection was lost. The heating, on the other hand, would go to a state where the situation before the interruption would be maintained (temperature setting).
Of course, the system must be built in such a way that if the connections are broken, no unwanted changes occur.
