i am currenting looking after an Ignition Installation on the Cloud. It works pretty good, Cloud servers have many redundancies and you can purchase backup servers in different cloud farms, so the could would not be the weak point, the weak point would be connection to the facility. I'd recommend if it is that important that you either have redundant internet path's or like mentioned above an Edge device. My preference would be Ignition Edge because then you can have a local client even if needed and it simplifies connecting to the cloud.