This is Cubase:
This is Studio One:
It is fairly common that I start many project templates without switching on some of my gear because I’m not planning to use it (eg. electronic drums, specific synths).
Studio One handles this elegantly. A warning is displayed but doesn’t interrupt the loading of the project. Cubase instead forces us to close every time the window.
You could add an option in the settings to suppress this pop up and display this warning in a window which closes automatically when the project is loaded. You could also leave a side window open in the project screen like Ableton does with a button to be able to correct those warnings if necessary. You could of course use that mechanism too to give users the option to to send bugs and crash dumps automatically if the application crashed last time.
PS. Studio One user already, only using Cubase as a MIDI editor when I’m at home.