As a developer, it would be great to be able to customize/set $globalAdminWarningMsg. This would allow us to use the already built-in functionality to display errors.
Currently, it can't be modified to show custom warnings or trigger on specific events. It would be useful in some cases - like if a module is incompatible with a specific setting in WHMCS. If that setting is set, the module should be able to set $globalAdminWarningMsg.
We can create custom notices in the Admin Area using the AdminAreaHeaderOutput hook but it would be cleaner to use the feature that already exists.