Include the option to create custom device classes via the UI.
That’s been possible for many years https://www.home-assistant.io/docs/configuration/customizing-devices#device_class
I meant user-customized device class.
For example: user create class “pump” defining icon_on, icon_off, state_on and state_on for use on any platform.
This allows for greater customization of user-created sensors.
Closing as a duplicate. This feature request was submitted later but has more detail: