You should try to separate the protobuf/grpc code from your Java code once and use it to integrate with your Java classes, which make most sense to you. There

You should try to separate the protobuf/grpc code from your Java code once and use it to integrate with your Java classes, which make most sense to you. There was a blog post around 3 months ago which went in this direction: use it to abstract transport/serialization, but don't try to force your whole business domain into this