Bobn4apples1
The GrapheneOS project is focused on security and privacy. This includes rapidly tracking security fixes from Google, and typically involves at least two releases per month (built for many devices). For technical reasons, this means that code added to the system that enables users to make configuration changes is expensive to maintain.
Other Android distributions have lots of user-configurable options (including selectable font families), but those distributions are typically months or years behind on security updates. It's a tradeoff.
Historically the GrapheneOS developers move quickly on clear, detailed reports of security and privacy problems, and from time to time add security and privacy improvements to the system. Also historically, the GrapheneOS developers do not move quickly to add user configuration options.
If a clear, detailed report is made about a security or privacy problem with the Wireless Emergency Alerts app, I think there's a good chance that appropriate changes will be made. In the other direction, I suspect that changes will not be made in the absence of a clear, detailed report about a security or privacy problem with the Wireless Emergency Alerts app.
If one wishes for a threat assessment of some part of GrapheneOS, it may be possible to hire a software security professional to carry one out. If one wishes a personal fork of GrapheneOS with specified changes that the GrapheneOS developers are not pursuing, it may be possible to hire somebody to make those changes.
Please note that I do not speak for the GrapheneOS project.