There is nothing preventing you having different base UUID for the service and characteristics. But in this case, as the base is different, you will have to refer to a different base for the characteristics and the service. And that should be the only difference.
I am not aware of any samples that does this, but as you refer to NUS here, you can take a look at the NUS client implementation in components/ble/ble_services/ble_nus_c/ble_nus_c.c. There you can see that the same base (referred to by the "type") is used for the service UUID's as for the characteristic UUID's. But you can just as well modify this implementation to use a different base UUID's for the characterisitcs as for the service.
So, essentially in addition to registering the base for the service with sd_ble_uuid_vs_add() (and getting a type for that), also register the base for the characteristics, and get the type for that. And the latter type is what you then refer to fro the characteristics.
I am not aware of any samples that does this, but as you refer to NUS here, you can take a look at the NUS client implementation in components/ble/ble_services/ble_nus_c/ble_nus_c.c. There you can see that the same base (referred to by the "type") is used for the service UUID's as for the characteristic UUID's. But you can just as well modify this implementation to use a different base UUID's for the characterisitcs as for the service.
So, essentially in addition to registering the base for the service with sd_ble_uuid_vs_add() (and getting a type for that), also register the base for the characteristics, and get the type for that. And the latter type is what you then refer to fro the characteristics.
