What even is a "model" if it doesn't have business logic? It sounds like you just want your model to be built from structs (that you call models) and procedures (that you call services). You can do that, but it can be quite hard to reason about what ways an entity can be updated, because any number of procedures could do it and all have their own ideas about what the business rules are. At this point your procedures might as well write back to the db themselves and just get rid of the "models".