The warning it there for the malicious cases, websites that try to pretend like they are your operating system (a full screen Windows 7 login window, for example) and make you enter your username and password into them, for example, so, no, I can hardly believe there will be a flag to remove this warning. Better be safe and a bit annoyed than sorry.
--kiosk sounds like exactly what you need, actually. Just change the shortcut to also have --kiosk when you launch the application.
If you worry about the lack of option to close the window, you can always create an extension that simply closes the window.