I use Glideapps to set up company wide alerts. Some alerts are relevant to only certain employees (special alerts). That is handled very well through the ‘filter rows user by signed in user’ feature on the layout tab. However there are several messages that apply to everyone (common alerts). Right now we have to duplicate the messages with each users id to ensure they receive the special alerts and the common alerts. It would be nice to have a feature (say the user column is left blank and has no specified sign in name) by which that row is visible to all users.
If you are using email and per user data, you should be able to leave the email blank for that particular alert and everybody should see it. I think exactly how you explained it is exactly how it should work.