This is more a change for integrations rather than blueprints since device_id’s are not user friendly.
The device selector does not allow you to filter out existing devices, so when used in a config flow you cannot filter out existing devices, the existing entity/filter selectors allow you to filter to just devices of a certain type matching a specified criteria, but not exclude specific devices.
This is specific for integrations that create additional entities for a device, where choosing a device should not show devices that have already been configured.
Parameters for include_devices and exclude_devices similar to how the entity selector implements them at an entity level would allow additional restrictions within the selector.